Scatterometry alignment for imprint lithography

ABSTRACT

Described are methods for patterning a substrate by imprint lithography. Imprint lithography is a process in which a liquid is dispensed onto a substrate. A template is brought into contact with the liquid and the liquid is cured. The cured liquid includes an imprint of any patterns formed in the template. Alignment of the template with a previously formed layer on a substrate, in one embodiment, is accomplished by using scatterometry.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a divisional patent application of U.S.patent application Ser. No. 10/210,785, filed Aug. 1, 2002 and entitled“Scatterometry Alignment for Imprints Lithography,” and listing MichaelP. C. Watts and Ian M. McMackin as inventors, the entirety of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments presented herein relate to methods and systems for imprintlithography. More particularly, embodiments relate to methods andsystems for micro- and nano-imprint lithography processes.

2. Description of the Relevant Art

Optical lithography techniques are currently used to make mostmicroelectronic devices. However, it is believed that these methods arereaching their limits in resolution. Sub-micron scale lithography hasbeen a critical process in the microelectronics industry. The use ofsub-micron scale lithography allows manufacturers to meet the increaseddemand for smaller and more densely packed electronic circuits on chips.It is expected that the microelectronics industry will pursue structuresthat are as small or smaller than about 50 nm. Further, there areemerging applications of nanometer scale lithography in the areas ofopto-electronics and magnetic storage. For example, photonic crystalsand high-density patterned magnetic memory of the order of terabytes persquare inch may require sub-100 nm scale lithography.

For making sub-50 nm structures, optical lithography techniques mayrequire the use of very short wavelengths of light (e.g., about 13.2nm). At these short wavelengths, many common materials are not opticallytransparent and therefore imaging systems typically have to beconstructed using complicated reflective optics. Furthermore, obtaininga light source that has sufficient output intensity at these wavelengthsis difficult. Such systems lead to extremely complicated equipment andprocesses that may be prohibitively expensive. It is also believed thathigh-resolution e-beam lithography techniques, though very precise, aretoo slow for high-volume commercial applications.

Several imprint lithography techniques have been investigated as lowcost, high volume manufacturing alternatives to conventionalphotolithography for high-resolution patterning. Imprint lithographytechniques are similar in that they use a template containing topographyto replicate a surface relief in a film on the substrate. One form ofimprint lithography is known as hot embossing.

Hot embossing techniques face several challenges: i) pressures greaterthan 10 MPa are typically required to imprint relief structures, ii)temperatures must be greater than the T_(g) of the polymer film, iii)patterns (in the substrate film) have been limited to isolation trenchesor dense features similar to repeated lines and spaces. Hot embossing isunsuited for printing isolated raised structures, such as lines anddots. This is because the highly viscous liquids resulting fromincreasing the temperature of the substrate films require extremely highpressures and long time durations to move the large volume of liquidsneeded to create isolated structures. This pattern dependency makes hotembossing unattractive. Also, high pressures and temperatures, thermalexpansion, and material deformation generate severe technical challengesin the development of layer-to-layer alignment at the accuracies neededfor device fabrication. Such pattern placement distortions lead toproblems in applications, such as patterned magnetic media for storageapplications. The addressing of the patterned medium bit by theread-write head becomes very challenging unless the pattern placementdistortions can be kept to a minimum.

SUMMARY OF THE INVENTION

In one embodiment, a patterned layer is formed by curing an activatinglight curable liquid disposed on a substrate in the presence of apatterned template. The patterned template is positioned over apredefined portion of the substrate. Typically, the predefined portionof the substrate includes a previously formed patterning area. Alignmentof the template with the substrate is accomplished with alignment markson both the template and substrate.

In an embodiment, a patterned template is placed in a spacedrelationship to the substrate. The patterned template includes analignment mark. The template alignment mark includes a diffractiongrating which matches a corresponding substrate alignment mark. Ascatterometry alignment system is coupled to the body such that thealignment of the template diffraction grating with the substratediffraction grating can be analyzed with the system. Alignment isaccomplished by illuminating the template alignment mark and thesubstrate alignment mark with light at an angle that is substantiallynormal to plane defined by the substrate. Light reflected along anon-zero order from the template and substrate alignment marks ismeasured. Light measurements include analyzing the intensity of light atmultiple wavelengths. Averaging out of light intensity readings atmultiple wavelengths is used to determine an average alignment error.The average alignment error may be used to alter the position of thetemplate with respect to the substrate prior to forming a patternedlayer.

In another embodiment, a patterned template is placed in a spacedrelationship to the substrate. The patterned template includes analignment mark. The template alignment mark includes a diffractiongrating which matches a corresponding substrate alignment mark.Alignment is accomplished by illuminating the template alignment markand the substrate alignment mark with two incident light beams at anangle that is substantially non-normal to plane defined by thesubstrate. Light reflected along the zero order from the template andsubstrate alignment marks is measured. Light measurements includeanalyzing the intensity of light at multiple wavelengths. Averaging outof light intensity readings at multiple wavelengths is used to determinean average alignment error. The average alignment error may be used toalter the position of the template with respect to the substrate priorto forming a patterned layer.

In another embodiment, a patterned template is placed in a spacedrelationship to the substrate. The patterned template includes analignment mark. The template alignment mark includes a diffractiongrating which matches a corresponding substrate alignment mark.Alignment is accomplished by illuminating the template alignment markand the substrate alignment mark with two incident light beams at anangle that is substantially non-normal to plane defined by thesubstrate. Light reflected along a non-zero order from the template andsubstrate alignment marks is measured. Light measurements includeanalyzing the intensity of light at multiple wavelengths. Averaging outof light intensity readings at multiple wavelengths is used to determinean average alignment error. The average alignment error may be used toalter the position of the template with respect to the substrate priorto forming a patterned layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings in which:

FIG. 1 depicts an embodiment of a system for imprint lithography;

FIG. 2 depicts an imprint lithography system enclosure;

FIG. 3 depicts an embodiment of an imprint lithography head coupled toan imprint lithography system;

FIG. 4 depicts a projection view of an imprint head;

FIG. 5 depicts an exploded view of an imprint head;

FIG. 6 depicts a projection view of a first flexure member;

FIG. 7 depicts a projection view of a second flexure member;

FIG. 8 depicts a projection view of first and second flexure memberscoupled together;

FIG. 9 depicts a projection view of a fine orientation system coupled toa pre-calibration system of an imprint head;

FIG. 10 depicts a cross-sectional view of a pre-calibration system;

FIG. 11 depicts a schematic diagram of a flexure system;

FIG. 12 depicts a projection view of a motion stage and an imprint headof an imprint lithography system;

FIG. 13 depicts a schematic diagram of a liquid dispense system;

FIG. 14 depicts a projection view of an imprint head with a light sourceand camera optically coupled to the imprint head;

FIGS. 15 and 16 depict side views of an interface between a liquiddroplet and a portion of a template;

FIG. 17 depicts a cross-sectional view of a first embodiment of templateconfigured for liquid confinement at the perimeter of the template;

FIG. 18 depicts a cross-sectional view of a second embodiment oftemplate configured for liquid confinement at the perimeter of thetemplate;

FIGS. 19A-19D depict cross-sectional views of a sequence of steps of atemplate contacting a liquid disposed on a substrate.

FIGS. 20A-20B depict top and cross-sectional views, respectively, of atemplate having a plurality of patterning areas and borders;

FIG. 21 depicts a projection view of a rigid template support systemcoupled to a pre-calibration system of an imprint head;

FIG. 22 depicts an imprint head coupled to an X-Y motion system;

FIGS. 23A-23F depict cross-sectional views of a negative imprintlithography process;

FIGS. 24A-24D depict cross-sectional views of a negative imprintlithography process with a transfer layer;

FIGS. 25A-25D depict cross-sectional views of a positive imprintlithography process;

FIGS. 26A-26C depict cross-sectional views of a positive imprintlithography process with a transfer layer;

FIGS. 27A-27E depict cross-sectional views of a combined positive andnegative imprint lithography process;

FIG. 28 depicts a schematic of an optical alignment measuring devicepositioned over a template and substrate;

FIG. 29 depicts a scheme for determining the alignment of a templatewith respect to a substrate using alignment marks by sequentiallyviewing and refocusing;

FIG. 30 depicts a scheme for determining the alignment of a templatewith respect to a substrate using alignment marks and polarized filters;

FIG. 31 depicts a top view of an alignment mark that is formed frompolarizing lines;

FIGS. 32A-32C depict top views of patterns of curable liquid applied toa substrate;

FIGS. 33A-33C depict a scheme for removing a template from a substrateafter curing;

FIG. 34 depicts an embodiment of a template positioned over a substratefor electric field based lithography;

FIGS. 35A-35D depict a first embodiment of a process for formingnanoscale structures using contact with a template;

FIGS. 36A-36C depict a first embodiment of a process for formingnanoscale structures without contacting a template;

FIGS. 37A-37C depict a template that includes a continuous patternedconductive layer disposed on a non-conductive base;

FIG. 38 depicts a motion stage having a substrate tilt module;

FIG. 39 depicts a motion stage that includes a fine orientation system;

FIG. 40 depicts a schematic drawing of a substrate support;

FIG. 41 depicts a schematic drawing of an imprint lithography systemthat includes an imprint head disposed below a substrate support;

FIG. 42 depicts a schematic view of the degrees of motion of thetemplate and the substrate;

FIG. 43 depicts a schematic view of an interferometer based positiondetector;

FIG. 44 depicts a projection view of a an interferometer based positiondetector;

FIG. 45 depicts a cross sectional view of a patterned template thatincludes an alignment mark surrounded by a border;

FIGS. 46A-46D depict schematic views of an off axis alignment method;

FIGS. 47A-47E depict overhead views of a theta alignment process;

FIG. 48A depicts a top view of an alignment target that includes adiffraction grating;

FIG. 48B depicts a cross-sectional view of an diffraction grating;

FIG. 48C depicts a top view of an alignment target that includesdiffraction gratings having different spacings;

FIG. 49 depicts a schematic view of a scatterometry system for analyzingmultiple wavelengths on N order scattered light;

FIG. 50 depicts a schematic view of a scatterometry system for analyzingmultiple wavelengths on N order scattered light through an opticalelement;

FIG. 51 depicts a schematic view of a scatterometry system for analyzingzero order scattered light at non-normal angles;

FIG. 52 depicts a schematic view of a scatterometry system for analyzingzero order scattered light at non-normal angles through opticalelements;

FIG. 53 depicts a schematic view of a scatterometry system for analyzingzero order scattered light at non-normal angles through a fiber opticsystem; and

FIG. 54 depicts a schematic view of a scatterometry system for analyzingN order scattered light at non-normal angles through a fiber opticsystem.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments presented herein generally relate to systems, devices, andrelated processes of manufacturing small devices. More specifically,embodiments presented herein relate to systems, devices, and relatedprocesses of imprint lithography. For example, these embodiments may beused for imprinting sub-100 nm features on a substrate, such as asemiconductor wafer. It should be understood that these embodiments mayalso be used to manufacture other kinds of devices including, but notlimited to, patterned magnetic media for data storage, micro-opticaldevices, micro-electromechanical system, biological testing devices,chemical testing and reaction devices, and X-ray optical devices.

Imprint lithography processes have demonstrated the ability to replicatehigh-resolution (e.g., sub-50 nm) images on substrates using templatesthat contain images as topography on their surfaces. Imprint lithographymay be used in patterning substrates in the manufacture ofmicroelectronic devices, optical devices, MEMS, opto-electronics,patterned magnetic media for storage applications, etc. Imprintlithography techniques may be superior to optical lithography for makingthree-dimensional structures such as micro lenses and T-gate structures.Components of an imprint lithography system, including the template,substrate, liquid and any other materials that may affect the physicalproperties of the system including, but not limited to, surface energy,interfacial energies, Hamacker constants, Van der Waals' forces,viscosity, density, opacity, etc., are engineered to properlyaccommodate a repeatable process.

Methods and systems for imprint lithography are discussed in U.S. Pat.No. 6,334,960 to Willson et al. entitled “Step and Flash ImprintLithography,” which is incorporated herein by reference. Additionalmethods and systems for imprint lithography are further discussed in thefollowing U.S. patent applications: U.S. Ser. No. 09/908,455 filed Jul.17, 2001 (published as U.S. Publication No. 2002-0094496 A1) entitled“Method and System of Automatic Fluid Dispensing for Imprint LithographyProcesses”; U.S. Ser. No. 09/907,512 filed Jul. 16, 2001 (issued as U.S.Pat. No. 6,921,615) entitled “High-Resolution Overlay Alignment Methodsand Systems for Imprint Lithography”; U.S. Ser. No. 09/920,341 filedAug. 1, 2001 (published as U.S. Publication No. 2002-0093122-A1)entitled “Methods for High-Precision Gap Orientation Sensing Between aTransparent Template and Substrate for Imprint Lithography”; U.S. Ser.No. 09/934,248 filed Aug. 21, 2001 (published as U.S. Publication No.2002-0150398-A1) entitled “Flexure Based Macro Motion TranslationStage”; U.S. Ser. No. 09/698,317 filed Oct. 27, 2000 (issued as U.S.Pat. No. 6,873,087) entitled “High-Precision Orientation Alignment andGap Control Stages for Imprint Lithography Processes”; U.S. Ser. No.09/976,681 filed Oct. 12, 2001 (issued as U.S. Pat. No. 6,696,220)entitled “Template Design for Room Temperature, Low Pressure Micro- andNano-Imprint Lithography”; and U.S. Ser. No. 10/136,188 filed May 1,2002 (published as U.S. Publication No. 2003-0205657-A1) entitled“Methods of Manufacturing a Lithography Template” to Voison; all ofwhich are incorporated herein by reference. Further methods and systemsare discussed in the following publications, all of which areincorporated herein by reference: “Design of Orientation Stages for Stepand Flash Imprint Lithography,” B. J. Choi, S. Johnson, M. Colburn, S.V. Sreenivasan, C. G. Willson, to appear in J. of Precision Engineering;“Large Area High Density Quantized Magnetic Disks Fabricated UsingNanoimprint Lithography,” W. Wu, B. Cui, X. Y. Sun, W. Zhang, L. Zhunag,and S. Y. Chou, J. Vac Sci Technol B 16 (6), 3825-3829,November-December 1998; “Lithographically-Induced Self-Assembly ofPeriodic Polymer Micropillar Arrays,” S. Y. Chou, L. Zhuang, J. Vac SciTechnol B 17 (6), 3197-3202, 1999; and “Large Area Domain Alignment inBlock Copolymer Thin Films Using Electric Fields,” P. Mansky, J.DeRouchey, J. Mays, M. Pitsikalis, T. Morkved, H. Jaeger and T. Russell,Macromolecules 13, 4399 (1998).

System for Imprint Lithography

Overall System Description

FIG. 1 depicts an embodiment of a system for imprint lithography 3900.Imprint lithography system 3900 includes an imprint head 3100. Imprinthead 3100 is mounted to an imprint head support 3910. Imprint head 3100is configured to hold a patterned template 3700. Patterned template 3700includes a plurality of recesses that define a pattern of features to beimprinted into a substrate. Imprint head 3100 or motion stage 3600 isfurther configured to move patterned template 3700 toward and away froma substrate to be imprinted during use. Imprint lithography system 3900also includes motion stage 3600. Motion stage 3600 is mounted to motionstage support 3920. Motion stage 3600 is configured to hold a substrateand move the substrate in a generally planar motion about motion stagesupport 3920. Imprint lithography system 3900 further includes anactivating light source 3500 coupled to imprint head 3100. Activatinglight source 3500 is configured to produce a curing light and direct theproduced curing light through patterned template 3700 coupled to imprinthead 3100. Curing light includes light at an appropriate wavelength tocure a polymerizable liquid. Curing light includes ultraviolet light,visible light, infrared light, x-ray radiation and electron beamradiation.

Imprint head support 3910 is coupled to motion stage support 3920 bybridging supports 3930. In this manner imprint head 3100 is positionedabove motion stage 3600. Imprint head support 3910, motion stage support3920 and bridging supports 3930 are herein collectively referred to asthe system “body.” The components of the system body may be formed fromthermally stable materials. Thermally stable materials have a thermalexpansion coefficient of less than about 10 ppm/° C. at about roomtemperature (e.g., 25° C.). In some embodiments, the material ofconstruction may have a thermal expansion coefficient of less than about10 ppm/° C., or less than 1 ppm/° C. Examples of such materials includesilicon carbide, certain alloys of iron, including but not limited to,certain alloys of steel and nickel (e.g., alloys commercially availableunder the name INVAR®), and certain alloys of steel, nickel and cobalt(e.g., alloys commercially available under the name SUPER INVAR™).Additional examples of such materials include certain ceramics,including but not limited to, ZERODUR® ceramic. Motion stage support3920 and bridging supports 3930 are coupled to a support table 3940.Support table 3940 provides a substantially vibration free support forthe components of imprint lithography system 3900. Support table 3940isolates imprint lithography system 3900 from ambient vibrations (e.g.,due to works, other machinery, etc.). Motion stages and vibrationisolation support tables are commercially available from NewportCorporation of Irvine, Calif.

As used herein, the “X-axis” refers to the axis that runs betweenbridging supports 3930. As used herein the “Y-axis” refers to the axisthat is orthogonal to the X-axis. As used herein the “X-Y plane” is aplane defined by the X-axis and the Y-axis. As used herein the “Z-axis”refers to an axis running from motion stage support 3920 to imprint headsupport 3910, orthogonal to the X-Y plane. Generally an imprint processinvolves moving the substrate, or the imprint head, along an X-Y planeuntil the proper position of the substrate with respect to patternedtemplate 3700 is achieved. Movement of the template, or motion stage3600, along the Z-axis, will bring patterned template 3700 to a positionthat allows contact between patterned template 3700 and a liquiddisposed on a surface of the substrate.

Imprint lithography system 3900 may be placed in an enclosure 3960, asdepicted in FIG. 2. Enclosure 3960 encompasses imprint lithographysystem 3900 and provides a thermal and air barrier to the lithographycomponents. Enclosure 3960 includes a movable access panel 3962 thatallows access to the imprint head 3100 and motion stage 3600 of FIG. 1when moved to an “open” position, as depicted in FIG. 2. When in a“closed” position, the components of imprint lithography system 3900 areat least partially isolated from the room atmosphere. Access panel 3962also serves as a thermal barrier to reduce the effects of temperaturechanges within the room on the temperature of the components withinenclosure 3960. Enclosure 3960 includes a temperature control system. Atemperature control system is used to control the temperature ofcomponents within enclosure 3960. In one embodiment, temperature controlsystem is configured to inhibit temperature variations of greater thanabout 1° C. within enclosure 3960. In some embodiments, a temperaturecontrol system inhibits variations of greater than about 0.1° C. In oneembodiment, thermostats or other temperature measuring devices incombination with one or more fans may be used to maintain asubstantially constant temperature within enclosure 3960.

Various user interfaces may also be present on enclosure 3960. Acomputer controlled user interface 3964 may be coupled to enclosure3960. User interface 3964 may depict the operating parameters,diagnostic information, job progress and other information related tothe functioning of the enclosed imprint system 3900. User interface 3964may also be configured to receive operator commands to alter theoperating parameters of imprint lithography system 3900. A stagingsupport 3966 may also be coupled to enclosure 3960. Staging support 3966is used by an operator to support substrates, templates and otherequipment during an imprint lithography process. In some embodiments,staging support 3966 may include one or more indentations 3967configured to hold a substrate (e.g., a circular indentation for asemiconductor wafer). Staging support 3966 may also include one or moreindentations 3968 for holding patterned template 3700, shown in FIG. 1.

Additional components may be present depending on the processes thatimprint lithography system 3900 is designed to implement. For example,for semiconductor processing equipment including, but not limited to, anautomatic wafer loader, an automatic template loader and an interface toa cassette loader (all not shown) may be coupled to imprint lithographysystem 3900.

Imprint Head

FIG. 3 depicts an embodiment of a portion of imprint head 3100. Imprinthead 3100 includes a pre-calibration system 3109 and a fine orientationsystem 3111 coupled to pre-calibration system 3109. Template support3130 is coupled to fine orientation system 3111. Template support 3130is designed to support and couple patterned template 3700 to fineorientation system 3111.

Referring to FIG. 4, a disk-shaped flexure ring 3124, which makes up aportion of pre-calibration system 3109 of FIG. 3, is coupled to imprinthead housing 3120. Imprint head housing 3120 is coupled to a middleframe 3114 with guide shafts 3112 a, 3112 b. In one embodiment, three(3) guide shafts may be used (the back guide shaft is not visible inFIG. 4) to provide a support for housing 3120. Sliders 3116A and 3116Bcoupled to corresponding guide shafts 3112 a, 3112 b about middle frame3114 are used to facilitate the up and down motion of housing 3120. Adisk-shaped base plate 3122 is coupled to the bottom portion of housing3120. Base plate 3122 may be coupled to flexure ring 3124. Flexure ring3124 supports fine orientation system 3111 components that include firstflexure member 3126 and second flexure member 3128. The operation andconfiguration of flexure members 3126, 3128 are discussed in detailbelow.

FIG. 5 depicts an exploded view of imprint head 3100. As shown in FIG.5, actuators 3134 a, 3134 b, and 3134 c are fixed within housing 3120and coupled to base plate 3122 and flexure ring 3124. In operation,motion of actuators 3134 a, 3134 b, and 3134 c controls the movement offlexure ring 3124. Motion of actuators 3134 a, 3134 b, and 3134 c mayallow for a coarse pre-calibration. In some embodiments, actuators 3134a, 3134 b, and 3134 c may be equally spaced around housing 3120.Actuators 3134 a, 3134 b, 3134 c and flexure ring 3124 together formpre-calibration system 3109, shown in FIG. 3. Actuators 3134 a, 3134 b,and 3134 c allow translation of flexure ring 3124 along the Z-axis tocontrol the gap accurately.

Imprint head 3100 also includes a mechanism that enables fineorientation control of patterned template 3700 so that properorientation alignment may be achieved and a uniform gap may bemaintained by patterned template 3700 with respect to a substratesurface. Alignment and gap control is achieved, in one embodiment, bythe use of first and second flexure members, 3126 and 3128,respectively.

FIGS. 6 and 7 depict embodiments of first and second flexure members,3126 and 3128, respectively, in more detail. As depicted in FIG. 6,first flexure member 3126 includes a plurality of flexure joints 3160coupled to corresponding rigid bodies 3164 and 3166. Flexure joints 3160may be notch shaped to provide motion of rigid bodies 3164 and 3166about pivot axes that are located along the thinnest cross-section ofthe flexure joints. Flexure joints 3160 and rigid body 3164 togetherform arm 3172, while additional flexure joints 3160 and rigid body 3166together form arm 3174. Arms 3172 and 3174 are coupled to and extendfrom first flexure frame 3170. First flexure frame 3170 has an opening3182, which allows curing light (e.g., ultraviolet light) to passthrough first flexure member 3126. In the depicted embodiment, fourflexure joints 3160 allow motion of first flexure frame 3170 about afirst orientation axis 3180. It should be understood, however, that moreor less flexure joints may be used to achieve the desired control. Firstflexure member 3126 is coupled to second flexure member 3128 throughfirst flexure frame 3170, as depicted in FIG. 8. First flexure member3126 also includes two coupling members 3184 and 3186. Coupling members3184 and 3186 include openings that allow attachment of the couplingmembers to flexure ring 3124, shown in FIG. 5, using any suitablefastening means. Coupling members 3184 and 3186 are coupled to firstflexure frame 3170 via arms 3172 and 3174, as depicted in FIG. 6.

Second flexure member 3128 includes a pair of arms 3202 and 3204extending from second flexure frame 3206, as depicted in FIG. 7. Flexurejoints 3162 and rigid body 3208 together form arm 3202, while additionalflexure joints 3162 and rigid body 3210 together form arm 3204. Flexurejoints 3162 may be notch shaped to provide motion of rigid body 3210 andarm 3204 about pivot axes that are located along the thinnestcross-section of the flexure joints 3162. Arms 3202 and 3204 are coupledto and extend from template support 3130. Template support 3130 isconfigured to hold and retain at least a portion of a patterned template3700, as described above. Template support 3130 also has an opening3212, which allows curing light (e.g., ultraviolet light) to passthrough second flexure member 3128. In the depicted embodiment, fourflexure joints 3162 allow motion of template support 3130 about a secondorientation axis 3200. It should be understood, however, that more orless flexure joints may be used to achieve the desired control. Secondflexure member 3128 also includes braces 3220 and 3222. Braces 3220 and3222 include openings that allow attachment of the braces to portions offirst flexure member 3126.

In one embodiment, first flexure member 3126 and second flexure member3128 are joined as shown in FIG. 8 to form fine orientation system 3111.Braces 3220 and 3222 are coupled to first flexure frame 3170 such thatfirst orientation axis 3180 of first flexure member 3126 and secondorientation axis 3200 of second flexure member 3128 are substantiallyorthogonal to each other. In such a configuration, first orientationaxis 3180 and second orientation axis 3200 intersect at a pivot point3252 at approximately the center region of patterned template 3700disposed in template support 3130 of FIG. 8. This coupling of the firstand second flexure members, 3126 and 3128, respectively, allows finealignment and gap control of patterned template 3700 during use. Whilefirst and second flexure members 3126 and 3128 are depicted as discreteelements, it should be understood that the first and second flexuremembers 3126 and 3128 may be formed from a single machined part wherethe flexure members 3126 and 3128 are integrated together. Flexuremembers 3126 and 3128 are coupled by mating of surfaces such that motionof patterned template 3700 occurs about pivot point 3252, substantiallyreducing “swinging” and other motions that may shear imprinted featuresfollowing imprint lithography. Fine orientation system 3111 impartsnegligible lateral motion at the template surface and negligibletwisting motion about the normal to the template surface due toselectively constrained high structural stiffness of the flexure joints3162. Another advantage of using the herein described flexure members3126 and 3120 is that they do not generate substantial amounts ofparticles, especially when compared with frictional joints. This offersan advantage for imprint lithography processes, as particles may disruptsuch processes.

FIG. 9 depicts the assembled fine orientation system 3111 coupled topre-calibration system 3109. Patterned template 3700 is positionedwithin template support 3130 that is part of second flexure member 3128.Second flexure member 3128 is coupled to first flexure member 3126 in asubstantially orthogonal orientation. First flexure member 3126 iscoupled to flexure ring 3124 via coupling members 3186 and 3184, shownin FIG. 6. Flexure ring 3124 is coupled to base plate 3122, as has beendescribed above.

FIG. 10 represents a cross-section of pre-calibration system 3109looking through cross-section 3260, shown in FIG. 9. As shown in FIG.10, flexure ring 3124 is coupled to base plate 3122 with actuator 3134.Actuator 3134 includes an end 3270 coupled to a force detector 3135 thatcontacts flexure ring 3124. During use activation of actuator 3134causes movement of end 3270 toward or away from flexure ring 3124. Themovement of end 3270 toward flexure ring 3124 induces a deformation offlexure ring 3124 and causes translation of fine orientation system3111, shown in FIG. 4, along the Z-axis toward the substrate. Movementof end 3270 away from flexure ring 3124 allows flexure ring 3124 to moveto its original shape and, in the process, moves fine orientation system3111, shown in FIG. 4, away from the substrate.

Referring to FIGS. 9 and 10, in a typical imprint process patternedtemplate 3700 is disposed in template support 3130 coupled to fineorientation system 3111. Patterned template 3700 is brought into contactwith a liquid on a surface of a substrate. Compression of the liquid onthe substrate as patterned template 3700 is brought closer to thesubstrate causes a resistive force to be applied by the liquid ontopatterned template 3700. This resistive force is translated through fineorientation system 3111 and to flexure ring 3124. The force appliedagainst flexure ring 3124 will also be translated as a resistive forceto actuator 3134. The resistive force applied to actuator 3134 may bedetermined using force detector 3135. Force detector 3135 may be coupledto actuator 3134 such that a resistive force applied to actuator 3134during use may be determined and controlled.

FIG. 11 depicts a flexure model 3300 useful in understanding theprinciples of operation of a fine decoupled orientation stage, such asfine orientation stage 3111 shown in FIG. 4. Flexure model 3300 mayinclude four parallel joints: Joints 1, 2, 3 and 4, that provide afour-bar-linkage system in its nominal and rotated configurations. Line3310 denotes an axis of alignment of Joints 1 and 2. Line 3312 denotesan axis of alignment of Joints 3 and 4. Angle α₁ represents an anglebetween a perpendicular axis through the center of patterned template3700 and line 3310. Angle α₂ represents a perpendicular axis through thecenter of patterned template 3700 and line 3310. Angles α₁ and α₂, insome embodiments, are selected so that the compliant alignment axis (ororientation axis) lies substantially at the surface of patternedtemplate 3700. For fine orientation changes, rigid body 3314 betweenJoints 2 and 3 may rotate about an axis depicted by Point C. Rigid body3314 may be representative of template support 3130 of second flexuremember 3128, shown in FIG. 9.

Referring to FIGS. 6-11, fine system 3111 generates pure tilting motionswith no substantial lateral motions at the surface of patterned template3700 coupled to fine orientation system 3111. The use of flexure arms3172, 3174, 3202, and 3204 may provide fine orientation system 3111 withhigh stiffness in the directions where side motions or rotations areundesirable and lower stiffness in directions where necessaryorientation motions are desirable. Fine orientation system 3111therefore allows rotations of template support 3130, and thereforepatterned template 3700, about pivot point 3252 at the surface ofpatterned template 3700, while providing sufficient resistance in adirection perpendicular to patterned template 3700 and parallel to thetemplate to maintain the proper position with respect to the substrate.In this manner a passive orientation system is used for orientation ofpatterned template 3700 to a parallel orientation with respect topatterned template 3700. The term “passive” refers to a motion thatoccurs without any user or programmable controller intervention, i.e.,the system self-corrects to a proper orientation by contact of patternedtemplate 3700 with the liquid. Alternate embodiments in which the motionof flexure arms 3172, 3174, 3202 and 3204 are controlled by motors toproduce an active flexure may also be implemented.

Motion of fine orientation system 3111 may be activated by direct orindirect contact with the liquid. If fine orientation system 3111 ispassive, then it is, in one embodiment, designed to have the mostdominant compliance about two orientation axes. The two orientation axeslie orthogonal to each other and lie on the imprinting surface of animprinting member disposed on fine orientation system 3111. The twoorthogonal torsional compliance values are set to be the same for asymmetrical imprinting member. A passive fine orientation system 3111 isdesigned to alter the orientation of patterned template 3700 when thetemplate is not parallel with respect to a substrate. When patternedtemplate 3700 makes contact with the liquid on the substrate, flexuremembers 3126 and 3128 compensate for the resulting uneven liquidpressure on patterned template 3700. Such compensation may be affectedwith minimal or no overshoot. Further, a fine orientation system 3111 asdescribed above may hold the substantially parallel orientation betweenpatterned template 3700 and the substrate for a sufficiently long periodto allow curing of the liquid.

Imprint head 3100 is mounted to imprint head support 3910, as depictedin FIG. 1. In this embodiment, imprint head support 3910 is mounted suchthat imprint head 3100 remains in a fixed position at all times. Duringuse, all movement along the X-Y plane is performed to the substrate bymotion stage 3600.

Motion Stage

Referring to FIG. 12, motion stage 3600 is used to support a substrateto be imprinted and move the substrate along an X-Y plane during use.Motion stage 3600, in some embodiments, is capable of moving a substrateover distances of up to several hundred millimeters with an accuracy ofat least ±30 nm, preferably with an accuracy of about ±10 nm. In oneembodiment, motion stage 3600 includes a substrate chuck 3610 that iscoupled to carriage 3620. Carriage 3620 is moved about a base 3630 on africtional bearing system or a non-frictional bearing system. In oneembodiment, a non-frictional bearing system that includes an air bearingis used. Carriage 3620 is suspended above base 3630 of motion stage 3600using, in one embodiment, an air layer (i.e., the “air bearing”).Magnetic or vacuum systems may be used to provide a counter balancingforce to the air bearing level. Both magnetic-based and vacuum-basedsystems are commercially available from a variety of suppliers and anysuch systems may be used in an imprint lithography process. One exampleof a motion stage that is applicable to imprint lithography processes isthe Dynam YX motion stage commercially available from NewportCorporation, Irvine Calif. Motion stage 3600 also may include a tip-tiltstage similar to the calibration stage, designed to approximately levelthe substrate to the X-Y motion plane. It also may include one or moretheta stages to orient the patterns on the substrate to the X-Y motionaxes.

Liquid Dispenser

Referring to FIGS. 1 and 13, imprint lithography system 3900 alsoincludes a liquid dispense system 3125 which is used to dispense acurable liquid onto a substrate. Liquid dispense system 3125 is coupledto the system body. In one embodiment, a liquid dispense system 3125 iscoupled to imprint head 3100. FIG. 3 depicts liquid dispenser head 2507of liquid dispense system 3125 extending out from cover 3127 of imprinthead 3100. Various components of liquid dispense system 3125 may bedisposed in cover 3127 of imprint head 3100.

A schematic of liquid dispense system 3125 is depicted in FIG. 13. In anembodiment, liquid dispense system 3125 includes a liquid container2501. Liquid container 2501 is configured to hold an activating lightcurable liquid. Liquid container 2501 is coupled to a pump 2504 viainlet conduit 2502. An inlet valve 2503 is positioned between liquidcontainer 2501 and pump 2504 to control flow through inlet conduit 2502.Pump 2504 is coupled to liquid dispenser head 2507 via outlet conduit2506.

Liquid dispense system 3125 is configured to allow precise volumecontrol of the amount of liquid dispensed onto an underlying substrate.In one embodiment, liquid control is achieved using a piezoelectricvalve as pump 2504. Piezoelectric valves are available commerciallyavailable from the Lee Company, Westbrook, Conn. During use, a curableliquid is drawn into pump 2504 through inlet conduit 2502. When asubstrate is properly positioned below, pump 2504 is activated to forcea predetermined volume of liquid through outlet conduit 2506. The liquidis then dispensed through liquid dispenser head 2507 onto the substrate.In this embodiment, liquid volume control is achieved by control of pump2504. Rapid switching of pump 2504 from an open to closed state allows acontrolled amount of liquid to be sent to liquid dispenser head 2507.Pump 2504 is configured to dispense liquid in volumes of less than about1 μL. The operation of pump 2504 may allow either droplets of liquid ora continuous pattern of liquid to be dispensed onto the substrate.Droplets of liquid are applied by rapidly cycling pump 2504 from an opento closed state. A stream of liquid is produced on the substrate byleaving pump 2504 in an open state and moving the substrate under liquiddispenser head 2507.

In another embodiment, liquid volume control may be achieved by use ofliquid dispenser head 2507. In such a system, pump 2504 is used tosupply a curable liquid to liquid dispenser head 2507. Small drops ofliquid whose volume may be accurately specified are dispensed using aliquid dispensing actuator. Examples of liquid dispensing actuatorsinclude micro-solenoid valves or piezo-actuated dispensers.Piezo-actuated dispensers are commercially available from MicroFabTechnologies, Inc., Plano, Tex. Liquid dispensing actuators areincorporated into liquid dispenser head 2507 to allow control of liquiddispensing. Liquid dispensing actuators are configured to dispensebetween about 50 pL to about 1000 pL of liquid per drop of liquiddispensed. Advantages of a system with a liquid dispensing actuatorinclude faster dispensing time and more accurate volume control. Liquiddispensing systems are further described in U.S. Ser. No. 09/908,455filed Jul. 17, 2001, entitled “Method and System of Automatic FluidDispensing for Imprint Lithography Processes,” which is incorporatedherein by reference.

Coarse Measurement System

Coarse determination of the position of patterned template 3700 and thesubstrate is determined by the use of linear encoders (e.g., exposedlinear encoders). Encoders offer a coarse measurement on the order of0.01 μm. Linear encoders include a scale coupled to the moving objectand a reader coupled to the body. The scale may be formed from a varietyof materials including glass, glass ceramics, and steel. The scaleincludes a number of markings that are read by the reader to determine arelative or absolute position of the moving object. The scale is coupledto motion stage 3600 by means that are known in the art. A reader iscoupled to the body and optically coupled to the scale. In oneembodiment, an exposed linear encoder may be used. Encoders may beconfigured to determine the position of motion stage 3600 along either asingle axis, or in a two-axis plane. An example of an exposed two-axislinear encoder is the PP model encoder available from HeidenhainCorporation, Schaumburg, Ill. Generally, encoders are built into manycommercially available X-Y motion stages. For example, the Dynam YXmotion stage available from Newport Corp. has a two-axis encoder builtinto the system.

Referring to FIG. 3, the coarse position of patterned template 3700along the Z-axis is also determined using a linear encoder. In oneembodiment, an exposed linear encoder may be used to measure theposition of patterned template 3700. A scale of the linear encoder, inone embodiment, is coupled to the pre-calibration ring of imprint head3100. Alternatively, the scale may be coupled directly to templatesupport 3130. The reader is coupled to the body and optically coupled tothe scale. Position of patterned template 3700 is determined along theZ-axis by use of encoders.

Interferometers

In some embodiments, the detection of the position of the template andsubstrate during an imprint lithography process needs to be known to adegree of accuracy of less than 100 nm. Since many features on apatterned template in a high-resolution semiconductor process aresmaller than 100 nm, such control is important to allow proper alignmentof the features. Fine position detection, in one embodiment, may bedetermined using interferometers (e.g., laser interferometers).

FIG. 42 depicts the axis of rotation and movement that may be determinedduring an imprint lithography process. The substrate position isdetermined along the X_(W) axis, the Y_(W) axis and the Z_(W) axis.Rotation of the substrate may also be determined about the X-axis(α_(W)), about the Y-axis (β_(W)) and about the Z-axis (θ_(W)).Similarly the position of the template is determined along the X, Y andZ axis. Rotation of the template may also be determined about the X-axis(α_(T)), about the Y-axis (β_(T)) and about the Z-axis (θ_(T)). Toproduce alignment of the template with the substrate the X, Y, and Zcoordinates, as well as the α, β and θ angles should be matched.

Linear encoders may be used to determine X-axis, Y-axis and Z-axispositions of the template and substrate. However, such encoderstypically do not provide the rotational information about these axes. Inone embodiment, interferometers may be used to determine the X-axis andY-axis position of the template and substrate and the rotational anglesα, β, and θ. A schematic of an interferometer based position detectionsystem is depicted in FIG. 43. An interferometer system 4300 includes afirst three axis laser interferometer 4310 and a second three axis laserinterferometer 4320. Mirror 4330 and mirror 4335 are coupled to thesubstrate and/or template. Mirror 4330 and mirror 4335 are opticallycoupled to first and second laser interferometers 4310 and 4320,respectively. Mirror 4330 is positioned on a portion of the templateand/or substrate that is perpendicular to a side that mirror 4335 isplaced on the template and/or substrate. As depicted in FIG. 43, thisallows five degrees of motion to be determined substantiallysimultaneously. First laser interferometer 4310 will provide sensing ofthe position of the substrate and/or template along the X-axis and therotational angles β and θ. Second laser interferometer 4320 will providesensing of the position of the substrate and/or template along theY-axis and the rotational angles α and θ.

An embodiment of an interferometer based position detector 4400 for usein imprint lithography system 3900, shown in FIG. 1, is depicted in FIG.44. Position detector 4400 is mounted to a portion of the body ofimprint lithography system 3900, shown in FIG. 1. For example, positiondetector 4440 may be mounted to support 3930 of the body. Positiondetector 4400 includes, in one embodiment, four interferometers.Interferometers are, in one embodiment, laser based. Either differentialor absolute interferometers may be used. Two interferometers 4410 and4415 are used for position determination of the template. The other twointerferometers 4420 and 4425 are used for position determination of thesubstrate. In one embodiment, all of the interferometers 4410, 4415,4420 and 4425 are three axis interferometers. The use of thisarrangement of interferometers 4410, 4415, 4420 and 4425 allows fivedegrees of movement (e.g., X and Y position and α, β and θ rotation) ofboth the template and the substrate. Laser 4430 provides light for theinterferometers. Light from the laser 4430 is conducted tointerferometers 4410, 4415, 4420, and 4425 through optical components4440 (note: not all optical components have been referenced). Opticalcomponents 4440 include beam splitters and mirror systems to conductlight from the laser 4430 to the interferometers 4410, 4415, 4420 and4425. Interferometer systems and the appropriate optical systems arecommercially available from several sources.

Air Gauges

In an embodiment, an air gauge 3135 may be coupled to imprint head 3100,as depicted in FIG. 3. Air gauge 3135 is used to determine whether asubstrate disposed on motion stage 3600 is substantially parallel to areference plane. As used herein, an “air gauge” refers to a device thatmeasures the pressure of a stream of air directed toward a surface. Whena substrate is disposed under an outlet of air gauge 3135, the distancethe substrate is from the outlet of air gauge 3135 will influence thepressure air gauge 3135 senses. Generally, the further away from airgauge 3135 the substrate is, the lesser the pressure.

In such a configuration, air gauge 3135 may be used to determinedifferences in pressure resulting from changes in the distance betweenthe substrate surface and air gauge 3135. By moving air gauge 3135 alongthe surface of the substrate, air gauge 3135 determines the distancebetween air gauge 3135 and the substrate surface at the various pointsmeasured. The degree of planarity of the substrate with respect to airgauge 3135 is determined by comparing the distance between air gauge3135 and the substrate at the various points measured. The distancebetween at least three points on the substrate and air gauge 3135 isused to determine if a substrate is planar. If the distance issubstantially the same, the substrate is considered to be planar.Significant differences in the distances measured between the substrateand air gauge 3135 indicate a non-planar relationship between thesubstrate and air gauge 3135. This non-planar relationship may be causedby the non-planarity of the substrate or a tilt of the substrate. Priorto use, a tilt of the substrate is corrected to establish a planarrelationship between the substrate and patterned template 3700. Suitableair gauges may be obtained from Senex Inc.

During use of air gauges, the substrate or patterned template 3700 isplaced within the measuring range of air gauge 3135. Motion of thesubstrate toward air gauge 3135 may be accomplished by either Z-axismotion of imprint head 3100 or Z-axis motion of motion stage 3600.

Light Source

In an imprint lithography process, a light curable liquid is disposed ona surface of the substrate. Patterned template 3700 is brought intocontact with the light curable liquid and activating light is applied tothe light curable liquid. As used herein “activating light” means lightthat may affect a chemical change. Activating light may includeultraviolet light (e.g., light having a wavelength between about 200 nmto about 400 nm), actinic light, visible light or infrared light.Generally, any wavelength of light capable of affecting a chemicalchange may be classified as activating. Chemical changes may bemanifested in a number of forms. A chemical change may include, but isnot limited to, any chemical reaction that causes a polymerization or across-linking reaction to take place. The activating light, in oneembodiment, is passed through patterned template 3700 prior to reachingthe composition. In this manner the light curable liquid is cured toform structures complementary to the structures formed on patternedtemplate 3700.

In some embodiments, activating light source 3500 is an ultravioletlight source capable of producing light having a wavelength betweenabout 200 nm to about 400 nm. Activating light source 3500 is opticallycoupled to patterned template 3700, as depicted in FIG. 1. In oneembodiment, activating light source 3500 is positioned proximate toimprint head 3100. Imprint head 3100 includes a mirror 3121, as depictedin FIG. 4, which reflects light from activating light source 3500 topatterned template 3700. Light passes through an opening in the body ofimprint head 3100 and is reflected by mirror 3121 toward patternedtemplate 3700. In this manner, activating light source 3500 irradiatespatterned template 3700 without being disposed in imprint head 3100.

Most activating light sources produce a significant amount of heatduring use. If activating light source 3500 is too close to imprintlithography system 3900, heat from the light source will radiate towardthe body of imprint lithography system 3900 and may cause thetemperature of portions of the body to increase. Since many metalsexpand when heated, the increase in temperature of a portion of the bodyof imprint lithography system 3900 may cause the body to expand. Thisexpansion may affect the accuracy of imprint lithography system 3900when sub-100 nm features are being produced.

In one embodiment, activating light source 3500 is positioned at asufficient distance from the body such that the system body is insulatedfrom heat produced by activating light source 3500 by the interveningair between activating light source 3500 and imprint head 3100. FIG. 14depicts activating light source 3500 optically coupled to imprint head3100. Activating light source 3500 includes an optical system 3510 thatprojects light generated by a light source toward imprint head 3100.Light passes from optical system 3510 into imprint head 3100 via opening3123. Light is then reflected toward patterned template 3700 coupled toimprint head 3100 by mirror 3121 disposed within the imprint head 3100(see FIG. 4). In this manner, the light source is thermally insulatedfrom the body. A suitable light source may be obtained from OAI Inc.,Santa Clara, Calif.

Optical Alignment Devices

Referring to FIG. 1, one or more optical measuring devices may beoptically coupled to imprint head 3100 and/or motion stage 3600.Generally, an optical measuring device is any device that allows theposition and/or orientation of patterned template 3700 with respect to asubstrate to be determined.

Turning to FIG. 14, a through-the-template optical imaging system 3800is optically coupled to imprint head 3100. Optical imaging system 3800includes an optical imaging device 3810 and an optical system 3820.Optical imaging device 3810, in one embodiment, is a CCD microscope.Optical imaging system 3800 is optically coupled to patterned template3700 through imprint head 3100. Optical imaging system 3800 is alsooptically coupled to a substrate, when the substrate is disposed underpatterned template 3700. Optical imaging system 3800 is used todetermine the placement error between patterned template 3700 and anunderlying substrate as described herein. In one embodiment, mirror 3121(depicted in FIG. 4) is movable within imprint head 3100. During analignment or optical inspection process, mirror 3121 is moved out of theoptical path of optical imaging system 3800.

During use of an optical alignment device, the substrate or patternedtemplate 3700 is placed within the measuring range (e.g., the field ofview) of optical imaging system 3800. Motion of the substrate towardoptical imaging system 3800 may be accomplished by either Z-axis motionof imprint head 3100 or Z-axis motion of motion stage 3600, shown inFIG. 7.

Additional optical imaging devices may be coupled to imprint head 3100for viewing the substrate in an off-axis position. Off-axis positionsare herein defined as a position that is not in the optical path of theactivating light source. An off-axis optical imaging system 3830 iscoupled to imprint head 3100 as depicted in FIG. 14. Off-axis opticalimaging system 3830 includes an optical imaging device 3832 and anoptical system 3834. Optical imaging device 3810, in one embodiment, isa CCD microscope. Off-axis optical imaging system 3830 is used to scanthe substrate without having patterned template 3700 in the opticalpath. Off-axis optical imaging system 3830 may be used for off-axisalignment processes as described herein. Additionally, off-axis opticalimaging system 3830 may be used to perform coarse alignment of patternedtemplate 3700 with the substrate, while through-the-template opticalimaging system 3800 is used for fine alignment of patterned template3700 with the substrate. Additional off-axis optical systems may becoupled to imprint head 3100. FIG. 12 depicts an additional off-axisoptical system 3840 coupled to imprint head 3100.

An additional optical imaging device may be coupled to the motion stagefor viewing patterned template 3700. A template optical imaging system3850 is coupled to motion stage 3600 as depicted in FIG. 12. Templateoptical imaging system 3850 includes an optical imaging device 3852 andan optical system 3854. Optical imaging device 3852, in one embodiment,is a CCD microscope. Template optical imaging system 3850 is used toscan the surface of patterned template 3700 without having to scanthrough the bulk of patterned template 3700. Template optical imagingsystem 3850 may be used for off-axis alignment processes as describedherein.

It should be understood that optical imaging systems may be disposed inalternate system embodiments described herein. For example, in analternate system embodiment, an optical imaging system may be coupled toa motion stage that is configured to move the imprint head. In suchembodiments, the substrate is mounted to a substrate support that alsoincludes an optical imaging device.

Light Curable Liquid

As previously mentioned, a light curable liquid is placed on a substrateand a template is brought into contact with the liquid during an imprintlithography process. The curable liquid is a low viscosity liquidmonomer solution. A suitable solution may have a viscosity ranging fromabout 0.01 cps to about 100 cps (measured at 25° C.). Low viscositiesare especially desirable for high-resolution (e.g., sub-100 nm)structures. Low viscosities also lead to faster gap closing.Additionally, low viscosities result in faster liquid filling of the gaparea at low pressures. In particular, in the sub-50 nm regime, theviscosity of the solution should be at or below about 30 cps, or morepreferably below about 5 cps (measured at 25° C.).

Many of the problems encountered with other lithography techniques maybe solved by using a low viscosity light curable liquid in an imprintlithography process. Patterning of low viscosity light curable liquidssolves each of the issues facing hot embossing techniques by utilizing alow-viscosity, light-sensitive liquid. Also use of a thick, rigid,transparent template offers the potential for easier layer-to-layeralignment. The rigid template is, in general, transparent to both liquidactivating light and alignment mark measurement light.

The curable liquid may be composed of a variety of polymerizablematerials. Generally, any photopolymerizable material may be used.Photopolymerizable materials may include a mixture of monomers and aphotoinitiator. In some embodiments, the curable liquid may include oneor more commercially available negative photoresist materials. Theviscosity of the photoresist material may be reduced by diluting theliquid photoresist with a suitable solvent.

In an embodiment, a suitable curable liquid includes a monomer, asilylated monomer, and an initiator. A crosslinking agent and a dimethylsiloxane derivative may also be included. Monomers include, but are notlimited to, acrylate and methacylate monomers. Examples of monomersinclude, but are not limited to, butyl acrylate, methyl acrylate, methylmethacrylate, or mixtures thereof. The monomer makes up approximately 25to 50% by weight of the curable liquid. It is believed that the monomerensures adequate solubility of the photoinitiator in the curable liquid.It is further believed that the monomer provides adhesion to anunderlying organic transfer layer, when used.

The curable liquid may also include a silylated monomer. Silylatedmonomers in general are polymerizable compounds that include a silicongroup. Classes of silylated monomers include, but are not limited to,silane acrylyl and silane methacrylyl derivatives. Specific examplesinclude methacryloxypropyl tris(tri-methylsiloxy)silane and(3-acryloxypropyl)tris(tri-methoxysiloxy)-silane. Silylated monomers maybe present in amounts from 25 to 50% by weight. The curable liquid mayalso include a dimethyl siloxane derivative. Examples of dimethylsiloxane derivatives include, but are not limited to, (acryloxypropyl)methylsiloxane dimethylsiloxane copolymer, acryloxypropyl methylsiloxanehomopolymer, and acryloxy terminated polydimethylsiloxane. Dimethylsiloxane derivatives are present in amounts from about 0 to 50% byweight. It is believed that the silylated monomers and the dimethylsiloxane derivatives may impart a high oxygen etch resistance to thecured liquid. Additionally, both the silylated monomers and the dimethylsiloxane derivatives are believed to reduce the surface energy of thecured liquid, therefore increasing the ability of the template torelease from the surface. The silylated monomers and dimethyl siloxanederivatives listed herein are all commercially available from Gelest,Inc.

Any material that may initiate a free radical reaction may be used asthe initiator. For activating light curing of the curable material, itis preferred that the initiator is a photoinitiator. Examples ofinitiators include, but are not limited to, alpha-hydroxyketones (e.g.,1-hydroxycyclohexyl phenyl ketone, sold by Ciba-Geigy Specialty ChemicalDivision as Irgacure 184), and acylphosphine oxide initiators (e.g.,phenylbis(2,4,6-trimethyl benzoyl) phosphine oxide, sold by Ciba-GeigySpecialty Chemical Division as Irgacure 819).

The curable liquid may also include a crosslinking agent. Crosslinkingagents are monomers that include two or more polymerizable groups. Inone embodiment, polyfunctional siloxane derivatives may be used as acrosslinking agent. An example of a polyfunctional siloxane derivativeis 1,3-bis(3-methacryloxypropyl)-tetramethyl disiloxane.

In one example, a curable liquid may include a mixture of 50% by weightof n-butyl acrylate and 50%(3-acryloxypropyl)tris-trimethylsiloxane-silane. To this mixture 3% byweight mixture of a 1:1 Irgacure 819 and Irgacure 184 and 5% of thecrosslinker 1,3-bis(3-methacryloxypropyl)-tetramethyl disiloxane may beadded. The viscosity of this mixture is less than 30 cps measured atabout 25° C.

Curable Liquid with Gas Release

In an alternate embodiment, the curable liquid may be formed of amonomer, an acid-generating photo-agent, and a base-generatingphoto-agent. Examples of the monomer include, but are not limited to,phenolic polymers and epoxy resins. The acid-generating photo-agent is acompound that releases acid when treated with activating light. Thegenerated acid catalyzes polymerization of the monomer. Those ofordinary skill in the art know such acid-generating additives, and thespecific acid-generating additive used depends on the monomer and thedesired curing conditions. In general, the acid-generating additive isselected to be sensitive to radiation at the first wavelength λ₁, which,in some implementations, is in the visible or near ultraviolet (near UV)range. For example, in some implementations, the first wavelength λ₁ isselected to be approximately 400 nm or longer. A base generatingphoto-agent is also added to the monomer. The base-generatingphoto-agent may inhibit curing of the monomer near the interface of thetemplate. The base generating photo-agent may be sensitive to radiationat a second wavelength λ₂, yet inert or substantially inert to radiationat the first wavelength λ₁. Moreover, the second wavelength λ₂ should beselected so that radiation at the second wavelength is primarilyabsorbed near the surface of the monomer at the interface with thetemplate and does not penetrate very far into the curable liquid. Forexample, in some implementations, a base generating additive that issensitive to radiation having a wavelength λ₂ in the deep UV range, inother words, radiation having a wavelength in the range of about 190-280nm, may be used.

According to an embodiment, a curable liquid that includes a monomer, anacid-generating photo-agent and a base-generating photo-agent isdeposited onto a substrate. A template is brought into contact with thecurable liquid. The curable liquid is then exposed to radiation at afirst wavelength λ₁ and a second wavelength λ₂ of light at substantiallythe same time. Alternatively, the curing liquid may be exposed to theradiation at the second wavelength λ₂ and subsequently to the radiationat the first wavelength λ₁. Exposure of the curable liquid to radiationat the second wavelength λ₂ produces an excess of base near theinterface with the template. The excess base serves to neutralize theacid that is produced by exposure of the curable liquid to radiation atthe first wavelength λ₁, thereby inhibiting the acid from curing thecurable liquid. Since the radiation at the second wavelength λ₂ has ashallow penetration depth into the curable liquid, the base produced bythat radiation only inhibits curing of the curable liquid at or near theinterface with the template. The remainder of the curable liquid iscured by exposure to the longer wavelength radiation (λ₁) whichpenetrates throughout the curable liquid. U.S. Pat. No. 6,218,316entitled “Planarization of Non-Planar Surfaces in Device Fabrication”describes additional details concerning this process and is incorporatedherein by reference.

In another embodiment, the curable liquid may include a photosensitiveagent which, when exposed, for example, to deep UV radiation, decomposesto produce one or more gases such as hydrogen (H₂), nitrogen (N₂),nitrous oxide (N₂O), sulfur tri-oxide (SO₃), acetylene (C₂H₂), carbondioxide (CO₂), ammonia (NH₃) or methane (CH₄). Radiation at a firstwavelength λ₁, such as visible or near UV, may be used to cure thecurable liquid, and the deep UV radiation (λ₂) may be used to produceone or more of the foregoing gases. The generation of the gases produceslocalized pressure near the interface between the cured liquid and thetemplate to facilitate separation of the template from the cured liquid.U.S. Pat. No. 6,218,316 describes additional details concerning thisprocess and is incorporated herein by reference.

In another embodiment, a curable liquid may be composed of a monomerthat cures to form a polymer that may be decomposed by exposure tolight. In one embodiment, a polymer with a doubly substituted carbonbackbone is deposited on the substrate. After the template is broughtinto contact with the curable liquid, the curable liquid is exposed toradiation at a first wavelength λ₁ (e.g., greater than 400 nm) andradiation at the second wavelength λ₂ in the deep UV range. Radiation atthe first wavelength serves to cure the curable liquid. When the curableliquid is exposed to the second wavelength λ₂, scission occurs at thesubstituted carbon atoms. Since deep UV radiation does not penetratedeeply into the curable liquid, the polymer decomposes only near theinterface with the template. The decomposed surface of the cured liquidfacilitates separation from the template. Other functional groups whichfacilitate the photo-decomposition of the polymer also can be used. U.S.Pat. No. 6,218,316 describes additional details concerning this processand is incorporated herein by reference.

Patterned Templates

In various embodiments, an imprint lithography template is manufacturedusing processes including, but not limited to, optical lithography,electron beam lithography, ion-beam lithography, x-ray lithography,extreme ultraviolet lithography, scanning probe lithography, focused ionbeam milling, interferometric lithography, epitaxial growth, thin filmdeposition, chemical etch, plasma etch, ion milling, reactive ion etchor a combination of the above. Methods for making patterned templatesare described in U.S. patent application Ser. No. 10/136,188 filed May1, 2002 entitled “Methods of Manufacturing a Lithography Template” toVoison which is incorporated herein by reference.

In an embodiment, the imprint lithography template is substantiallytransparent to activating light. The template includes a body having alower surface. The template further includes a plurality of recesses onthe lower surface extending toward the top surface of the body. Therecesses may be of any suitable size, although typically at least aportion of the recesses has a feature size of less than about 250 nm.

With respect to imprint lithography processes, the durability of thetemplate and its release characteristics may be of concern. In oneembodiment, a template is formed from quartz. Other materials may beused to form the template and include, but are not limited to: silicongermanium carbon, gallium nitride, silicon germanium, sapphire, galliumarsinide, epitaxial silicon, poly-silicon, gate oxide, silicon dioxideor combinations thereof. Templates may also include materials used toform detectable features, such as alignment markings. For example,detectable features may be formed of SiO_(x), where X is less than 2. Insome embodiments, X is about 1.5. In another example, detectablefeatures may be formed of a molybdenum silicide. Both SiOx andmolybdenum silicide are optically transparent to light used to cure thepolymerizable liquid. Both materials, however, are substantially opaqueto visible light. Use of these materials allows alignment marks to becreated on the template that will not interfere with curing of theunderlying substrate.

As previously mentioned, the template is treated with a surfacetreatment material to form a thin layer on the surface of the template.A surface treatment process is optimized to yield a low surface energycoating. Such a coating is used in preparing imprint templates forimprint lithography. Treated templates have desirable releasecharacteristics relative to untreated templates. Untreated templatesurfaces possess surface free energies of about 65 dynes/cm or more. Atreatment procedure disclosed herein yields a surface treatment layerthat exhibits a high level of durability. Durability of the surfacetreatment layer allows a template to be used for numerous imprintswithout having to replace the surface treatment layer. The surfacetreatment layer, in some embodiments, reduces the surface free energy ofthe lower surface measured at 25° C. to less than about 40 dynes/cm, orin some cases, to less than about 20 dynes/cm.

A surface treatment layer, in one embodiment, is formed by the reactionproduct of an alkylsilane, a fluoroalkylsilane, or afluoroalkyltrichlorosilane with water. This reaction forms a silinatedcoating layer on the surface of the patterned template. For example, asilinated surface treatment layer is formed from a reaction product oftridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane with water. Asurface treatment layer may be formed using either a liquid-phaseprocess or a vapor-phase process. In a liquid-phase process, thesubstrate is immersed in a solution of precursor and solvent. In avapor-phase process, a precursor is delivered via an inert carrier gas.It may be difficult to obtain a purely anhydrous solvent for use in aliquid-phase treatment. Water in the bulk phase during treatment mayresult in clump deposition, which will adversely affect the finalquality or coverage of the coating. In an embodiment of a vapor-phaseprocess, the template is placed in a vacuum chamber, after which thechamber is cycle-purged to remove excess water. Some adsorbed water,however, remains on the surface of the template. A small amount ofwater, however, is believed to be needed to initiate a surface reaction,which forms the coating. It is believed that the reaction may bedescribed by the formula:R—SiCl₃+3H₂O=>R—Si(OH)₃+3HCl

To facilitate the reaction, the template is brought to a desiredreaction temperature via a temperature-controlled chuck. The precursoris then fed into the reaction chamber for a prescribed time. Reactionparameters such as template temperature, precursor concentration, flowgeometries, etc. are tailored to the specific precursor and templatesubstrate combination. By controlling these conditions, the thickness ofthe surface treatment layer is controlled. The thickness of the surfacetreatment layer is kept at a minimal value to minimize the interferenceof the surface treatment layer with the feature size. In one embodiment,a monolayer of the surface treatment layer is formed.

Discontinuous Template

In an embodiment, there are at least two separate depths associated withthe recesses on the lower surface of patterned template 3700. FIGS. 20Aand 20B depict top and cross-sectional views, respectively, of apatterned template with recesses having two depths. Referring to FIGS.20A and 20B, a template includes one or more patterning areas 401. Insuch embodiments, a first relatively shallow depth is associated withthe recesses in patterning areas 401 of the template, as depicted inFIG. 20B. Patterning areas 401 include the area replicated duringpatterning of the template. Patterning areas 401 are positioned within aregion defined by the edges 407 of the template. Outer region 409 isdefined as the region that extends from an outer edge of any ofpatterning areas 401 to the edge of the template. The outer region has adepth that is substantially greater than the depth of the recesses inpatterning areas 401. The perimeter of the template is herein defined asthe patterning areas that are confined by outer region 409. As depictedin FIG. 20A, four patterning areas are positioned within the areadefined by the template. Patterning areas 401 are separated from theedges 407 of the template by outer region 409. The “perimeter” of thetemplate is defined by edges 403 a, 403 b, 403 c, 403 d, 403 e, 403 f,403 g, and 403 h of patterning areas 401.

Patterning areas 401 may be separated from each other by border regions405. Borders regions 405 are recesses that are positioned betweenpatterning areas 401 that have a greater depth than the recesses of thepattering areas. As described below, both border region 405 and outerregion 409 inhibits the flow of liquid between patterning areas 401 orbeyond the perimeter of patterning areas 401, respectively.

The design of the template is chosen based on the type of lithographyprocess used. For example, a template for positive imprint lithographyhas a design that favors the formation of discontinuous films on thesubstrate. In one embodiment, a template 12 is formed such that thedepth of one or more structures is relatively large compared to thedepth of structures used to form the patterning region, as depicted inFIG. 15. During use, template 12 is placed in a desired spacedrelationship to substrate 20. In such an embodiment, the gap (h₁)between the lower surface 536 of template 12 and substrate 20 is muchsmaller than the gap (h₂) between recessed surface 534 and substrate 20.For example, h₁ may be less than about 200 nm, while h₂ may be greaterthan about 10,000 nm. When template 12 is brought into contact withcurable liquid 40 on substrate 20, curable liquid 40 leaves the regionunder recessed surface 534 and fills the gap between lower surface 536and substrate 20 (as depicted in FIG. 16). It is believed thatcombinations of surface energies and capillary forces draw curableliquid 40 from the larger recess into the narrower region. As h₁ isdecreased, forces applied to curable liquid 40 by template 12 mayovercome capillary forces drawing curable liquid 40 under lower surface536. These forces may cause spreading of curable liquid 40 into the areaunder recessed surface 534. The minimum value of h₁ at which curableliquid 40 is inhibited from spreading into a recess 532 is referred toherein as the “minimum film thickness.” Additionally, as h₁ increases,the capillary forces are reduced, eventually allowing curable liquid 40to spread into the deeper recessed regions. The maximum value of h₁ atwhich the capillary forces are sufficient to inhibit flow of curableliquid 40 into the deeper recessed region is herein known as the“maximum film thickness.”

As depicted in FIGS. 17 and 18, in various embodiments, template 12 isformed such that a curable liquid placed on substrate 20 is inhibitedfrom flowing beyond perimeter 412 of template 12. In the embodimentdepicted in FIG. 17, height h₁ is measured from substrate 20 to shallowrecessed surface 552. Shallow recessed surface 552 extends to theperimeter of template 12. Thus, the edge of template 12 forms the heighth₂ and is effectively infinite in comparison to height h₁. In theembodiment depicted in FIG. 18, a deep recess is formed at the outeredge of template 12. Height h₂ is measured between substrate 20 and deeprecessed surface 554. Height h₁ is again measured between substrate 20and shallow recessed surface 552. In either embodiment, height h₂ ismuch larger than height h₁. If h₁ is small enough, the activating lightcurable liquid remains in the gap between template 12 and substrate 20while a curing agent is applied. Deeply recessed portions areparticularly useful for liquid confinement in step and repeat processesas described herein.

In an embodiment, template 12 and substrate 20 each have one or morealignment marks. Alignment marks may be used to align template 12 andsubstrate 20. For example, one or more optical imaging devices (e.g.,microscopes, cameras, imaging arrays, etc.) are used to determinealignment of the alignment marks.

In some embodiments, an alignment mark on the template may besubstantially transparent to activating light. Alternatively, thealignment mark may be substantially opaque to alignment mark detectionlight. As used herein, alignment mark detection light and light used forother measurement and analysis purposes is referred to as “analyzinglight.” In an embodiment, analyzing light includes, but is not limitedto, visible light and/or infrared light. The alignment mark may beformed of a material different than the material of the body. Forexample, the alignment mark may be formed from SiO_(x), where x is about1.5. In another example, the alignment mark may be formed of molybdenumsilicide. Alternately, the alignment mark may include a plurality oflines etched on a surface of the body. The lines are configured tosubstantially diffuse activating light, but produce an analyzable markunder analyzing light.

In various embodiments, one or more deep recesses as described above mayproject entirely through the body of the template to form openings inthe template. An advantage of such openings is that they may effectivelyensure that height h₂ is very large with respect to h₁ at each opening.Additionally, in some embodiments, pressurized gas or vacuum may beapplied to the openings. Pressurized gas or vacuum may also be appliedto one or more openings after curing the liquid. For example,pressurized gas may be applied after curing as part of a peel and pullprocess to assist in separating the template from the cured liquid.

In one embodiment, one or more alignment marks may be formed in apatterned template. As described herein, alignment marks formed in thetemplate may be used to align a template with a patterned area on asubstrate. One embodiment of a template that includes alignment marks isdepicted in FIG. 45. Patterned template 4500 includes patterning areas4510, alignment marks 4520, and alignment mark patterning area 4530.Alignment marks 4520 are separated from patterning areas 4510 and 4512by borders 4540 and 4542, respectively. Borders 4540 and 4542 have adepth that is substantially greater than the depth of alignment marks4520. When patterned template 4500 is brought into contact withactivating light curable liquid 4560, activating light curable liquid4560 spreads to the patterning areas 4510 and 4512, but is inhibitedfrom spreading into alignment marks 4520 area by the borders 4540 and4542, as depicted in FIG. 45.

Keeping the activating light curable liquid out of the alignment areamay offer advantages when alignment measurements are being taken. Duringa typical alignment procedure, optical measurements are taken thoroughthe template to the underlying substrate alignment marks (e.g.,alignment marks 4550) to determine if the alignment marks are aligned.The presence of a liquid between the template and the substrate duringalignment measurements, may interfere with optical measurements.Typically the index of refraction of a liquid is substantially similarto the template material. By keeping the liquid out of the alignmentregion, optical alignment techniques may be simplified and the opticalrequirements of the alignment systems reduced.

When a template is used for imprinting one of multiple layers to beformed on a substrate, it is advantageous that the template not onlyinclude an alignment mark for alignment with an underlying substrate,but also an alignment patterning area. As depicted in FIG. 45, alignmentmark patterning area 4530 contacts a portion of the applied activatinglight curable liquid. During curing, the alignment mark defined byalignment mark patterning area 4530 is imprinted into the cured layer.During subsequent processing, the alignment mark formed from alignmentmark patterning area 4530 may be used to assist in alignment of atemplate with the substrate.

Alternate System Embodiments

The above described imprint lithography system 3900 may be modifiedaccording to alternate embodiments discussed below. It should beunderstood that any of the described alternative embodiments may becombined, singly or in combination, with any other system describedherein.

Referring to FIG. 4, as described above, imprint head 3100 includes fineorientation system 3111 that allows for a “passive” orientation ofpatterned template 3700 with respect to the substrate. In anotherembodiment, fine orientation system 3111 may include actuators 3134 a,3134 b, and 3134 c coupled to flexure arms 3172, 3174, 3202, and 2304.Actuators 3134 a, 3134 b, and 3134 c may allow “active” control of fineorientation system 3111. During use an operator or a programmablecontroller monitors the orientation of patterned template 3700 withrespect to the substrate. The operators or a programmable controllerthen alters the orientation of patterned template 3700 with respect tothe substrate by operating actuators 3134 a, 3134 b, and 3134 c.Movement of actuators 3134 a, 3134 b and 3134 c causes motion of flexurearms 3172, 3174, 3202, and 3204 to alter the orientation of patternedtemplate 3700§. In this manner an “active” control of fine positioningof patterned template 3700 with respect to the substrate may beachieved. An active fine orientation system is further described in U.S.Ser. No. 09/920,341 filed Aug. 1, 2001 entitled “Methods forHigh-Precision Gap Orientation Sensing Between a Transparent Templateand Substrate for Imprint Lithography,” which is incorporated herein byreference.

Referring to FIG. 3, in an alternate embodiment, imprint head 3100 mayinclude a pre-calibration system 3109, as described above.Pre-calibration system 3109 includes a flexure ring 3124, as depicted inFIG. 21. In place of fine orientation system 3100 as described above,template support system 8000 is coupled to a pre-calibration ring. Incontrast to fine orientation system 3100, template support system 8000is formed of substantially rigid and non-compliant members 3127. Thesemembers provide a substantially rigid support for patterned template3700 disposed in template support 3130. In this embodiment, fineorientation may be achieved using motion stage 3600, shown in FIG. 1,instead of template support 3130.

In previous embodiments, imprint head 3100 is coupled to the body in afixed position. In an alternate embodiment, imprint head 3100 may bemounted to a motion system that allows imprint head 3100 to be movedalong the X-Y plane, as depicted in FIG. 22. Imprint head 3100 isconfigured to support patterned template 3700 as described in any of theembodiments herein. Imprint head 3100 is coupled to a motion system thatincludes an imprint head chuck 3110 and imprint motion stage 3123.Imprint head 3100 is mounted to imprint head chuck 3110. Imprint headchuck 3110 interacts with imprint motion stage 3123 to move imprint head3100 along an X-Y plane. Mechanical or electromagnetic motion systemsmay be used. Electromagnetic systems rely on the use of magnets toproduce an X-Y planar motion in imprint head chuck 3110. Generally, anelectromagnetic system incorporates permanent and electromagneticmagnets into imprint motion stage 3123 and imprint head chuck 3110. Theattractive forces of these magnets is overcome by a cushion of airbetween imprint head chuck 3110 and imprint motion stage 3123 such thatan “air bearing” is produced. Imprint head chuck 3110, and thereforeimprint head 3100, is moved along an X-Y plane on a cushion of air.Electromagnetic X-Y motion stages are described in further detail inU.S. Pat. No. 6,389,702, entitled “Method and Apparatus for MotionControl,” which is incorporated herein by reference. In a mechanicalmotion system, imprint head chuck 3110 is attached to imprint motionstage 3123. Imprint motion stage 3123 is then moved by use of variousmechanical means to alter the position of imprint head chuck 3110, andthus imprint head 3110, along the X-Y plane. In this embodiment, imprinthead 3100 may include a passive compliant fine orientation system, anactuated fine orientation system, or a rigid template support system, asdescribed herein.

With imprint head 3100 coupled to a moving support, the substrate may bemounted to a stationary support. Thus, in an alternate embodiment,imprint head 3100 is coupled to an X-Y axis motion stage as describedherein. A substrate is mounted to a substantially stationary substratesupport. A stationary substrate support 3640 is depicted in FIG. 40.Stationary substrate support 3640 includes a base 3642 and a substratechuck 3644. Substrate chuck 3644 is configured to support a substrateduring imprint lithography processes. Substrate chuck 3644 may employany suitable means to retain a substrate to substrate chuck 3644. In oneembodiment, substrate chuck 3644 may include a vacuum system whichapplies a vacuum to the substrate to couple the substrate to substratechuck 3644. Substrate chuck 3644 is coupled to base 3642. Base 3642 iscoupled to motion stage support 3920 of imprint lithography system 3900(see FIG. 1). During use, stationary substrate support 3640 remains in afixed position on motion stage support 3920 while imprint head 3100position is varied to access different portions of the substrate.

Coupling an imprint head to a motion stage can offer advantages overtechniques in which the substrate is on a motion stage. Motion stagesgenerally rely on an air bearing to allow substantially frictionlessmotion of the motion stage. Generally, motion stages are not designed toaccommodate significant pressure applied along the Z-axis. When pressureis applied to a motion stage chuck along the Z-axis, the motion stagechuck position will change slightly in response to this pressure. Duringa step and repeat process, a template that has a smaller area than thearea of the substrate is used to form multiple imprinted areas. Thesubstrate motion stage is relatively large compared to the template toaccommodate the larger substrates. When a template contacts thesubstrate motion stage in a position that is off-center, the motionstage will tilt to accommodate the increased pressure. This tilt iscompensated for by tilting the imprint head to ensure proper alignment.If, however, the imprint head is coupled to the motion stage, all of theforces along the Z-axis will be centered on the template, regardless ofwhere on the substrate the imprinting is taking place. This leads toincreased ease in alignment and may also increase the throughput of thesystem.

In an embodiment, a substrate tilt module 3654 may be formed insubstrate support 3650, as depicted in FIG. 38. Substrate support 3650includes a substrate chuck 3652, coupled to substrate tilt module 3654.Substrate tilt module 3654 is coupled to a base 3656. Base 3656, in oneembodiment, is coupled to a motion stage which allows X-Y motion ofsubstrate support 3650. Alternatively, base 3656 is coupled to a support(e.g., 3920) such that substrate support 3650 is mounted to imprintlithography system 3900, shown in FIG. 1 in a fixed position.

Substrate chuck 3652 may employ any suitable means to retain a substrateto substrate chuck 3652. In one embodiment, substrate chuck 3652 mayinclude a vacuum system which applies a vacuum to the substrate tocouple the substrate to substrate chuck 3652. Substrate tilt module 3654includes a flexure ring 3658 coupled to flexure ring support 3660. Aplurality of actuators 3662 are coupled to flexure ring 3658 and flexurering support 3660. Actuators 3662 are operated to alter the tilt offlexure ring 3658. Actuators 3662, in one embodiment, use a differentialgear mechanism that may be manually or automatically operated. In analternate embodiment, actuators 3662 use an eccentric roller mechanism.An eccentric roller mechanism generally provides more vertical stiffnessto substrate support 3650 than a differential gear system. In oneembodiment, substrate tilt module 3654 has a stiffness that will inhibittilt of the substrate when the template applies a force of between about1 lb. to about 10 lbs. to a liquid disposed on the substrate.Specifically, substrate tilt module 3654 is configured to allow no morethan 5 micro radians of tilt when pressure up to about 10 lbs. isapplied to the substrate through the liquid on the template.

During use sensors coupled to substrate chuck 3652 may be used todetermine the tilt of the substrate. The tilt of the substrate isadjusted by actuators 3662. In this manner tilt correction of thesubstrate may be achieved.

Substrate tilt module 3654 may also include a fine orientation system. Asubstrate support that includes a fine orientation system is depicted inFIG. 39. To achieve fine orientation control, flexure ring 3658 includesa central recess in which substrate chuck 3652 is disposed. The depth ofthe central recess is such that an upper surface of a substrate disposedon substrate chuck 3652 is substantially even with an upper surface offlexure ring 3658. Fine orientation may be achieved using actuators 3662capable of controlled motion in the nanometer range. Alternatively, fineorientation may be achieved in a passive manner. Actuators 3662 may besubstantially compliant. The compliance of actuators 3662 may allow thesubstrate to self-correct for variations in tilt when a template is incontact with a liquid disposed on a substrate surface. By disposing thesubstrate in a position that is substantially even with flexure ring3658, fine orientation may be achieved at the substrate-liquid interfaceduring use. Compliance of actuators 3662 is thus transferred to theupper surface of the substrate to allow fine orientation of thesubstrate.

The above-described systems are generally configured to systems in whichan activating light curable liquid is dispensed onto a substrate and thesubstrate and template are brought into proximity to each other. Itshould be understood, however, that the above-described systems may bemodified to allow an activating light curable liquid to be applied to atemplate rather than the substrate. In such an embodiment, the templateis placed below the substrate. FIG. 41 depicts a schematic drawing of anembodiment of a system 4100 that is configured such that the template ispositioned below a substrate. System 4100 includes an imprint head 4110and a substrate support 4120 positioned above imprint head 4110. Imprinthead 4110 is configured to hold patterned template 3700. Imprint head4110 may have a similar design to any of the herein described imprintheads. For example, imprint head 4110 may include a fine orientationsystem as described herein. Imprint head 4110 is coupled to imprint headsupport 4130. Imprint head 4110 may be coupled in a fixed position andremain substantially motionless during use. Alternatively, imprint head4110 may be placed on a motion stage that allows X-Y planar motion ofimprint head 4110 during use.

The substrate to be imprinted is mounted onto a substrate support 4120.Substrate support 4120 has a similar design to any of the hereindescribed substrate supports. For example, substrate support 4120 mayinclude a fine orientation system as described herein. Substrate support4120 may be coupled to a support 4140 in a fixed position and remainsubstantially motionless during use. Alternatively, substrate support4120 may be placed on a motion stage that allows X-Y planar motion ofsubstrate support during use.

During use an activating light curable liquid is placed on patternedtemplate 3700 disposed in imprint head 4110. The template may bepatterned or planar, depending on the type of operation to be performed.Patterned templates may be configured for use in positive, negative, orcombinations of positive and negative imprint lithography systems asdescribed herein.

Imprint Lithography Processes

Negative Imprint Lithography Process

A typical imprint lithography process is shown in FIGS. 23A-23F. Asdepicted in FIG. 23A, template 12 is positioned in a spaced relation tothe substrate 20 such that a gap 31 is formed between template 12 andsubstrate 20. Template 12 may include a surface that defines one or moredesired features, which may be transferred to substrate 20 duringpatterning. As used herein, a “feature size” generally refers to awidth, length and/or depth of one of the desired features. In variousembodiments, the desired features may be defined on the surface oftemplate 12 as recesses and/or a conductive pattern formed on a surfaceof template 12. Surface 14 of template 12 may be treated with a thinsurface treatment layer 13 that lowers template 12 surface energy andassists in separation of template 12 from substrate 20. Surfacetreatment layers for templates are described herein.

In an embodiment, curable liquid 40 may be dispensed upon substrate 20prior to moving template 12 into a desired position relative tosubstrate 20. Curable liquid 40 may be a curable liquid that conforms tothe shape of desired features of template 12. In an embodiment, curableliquid 40 is a low viscosity liquid that at least partially fills thespace of gap 31 without the use of high temperatures. Low viscosityliquids may also allow gap 31 between template 12 and substrate 20 to beclosed without requiring high pressures. As used herein, the term “lowviscosity liquids” refer to liquids having a viscosity of less thanabout 30 centipoise measured at about 25° C. Further details regardingappropriate selections for curable liquid 40 are discussed below.Template 12 may interact with curable liquid 40 to conform curableliquid 40 into a desire shape. For example, curable liquid 40 mayconform to the shape of template 12, as depicted in FIG. 23B. Theposition of template 12 may be adjusted to create a desired gap distancebetween template 12 and substrate 20. The position of template 12 mayalso be adjusted to properly align template 12 with substrate 20.

After template 12 is properly positioned, curable liquid 40 is cured toform a masking layer 42 on substrate 20. In an embodiment, curableliquid 40 is cured using activating light 32 to form masking layer 42.Application of activating light 32 through template 12 to cure curableliquid 40 is depicted in FIG. 23C. After curable liquid 40 issubstantially cured, template 12 is removed from masking layer 42,leaving cured masking layer 42 on the surface of substrate 20, asdepicted in FIG. 23D. Masking layer 42 has a pattern that iscomplementary to the pattern of template 12. Masking layer 42 mayinclude a “base layer” (also called a “residual layer”) between one ormore desired features. The separation of template 12 from masking layer42 is done so that desired features remain intact without shearing ortearing from the surface of substrate 20. Further details regardingseparation of template 12 from substrate 20 following imprinting arediscussed below.

Masking layer 42 may be used in a variety of ways. For example, in someembodiments, masking layer 42 may be a functional layer. In suchembodiments, curable liquid 40 may be curable to form a conductivelayer, a semiconductive layer, a dielectric layer and/or a layer havinga desired mechanical or optical property. In another embodiment, maskinglayer 42 may be used to cover portions of substrate 20 during furtherprocessing of substrate 20. For example, masking layer 42 may be usedduring a material deposition process to inhibit deposition of thematerial on certain portions of the substrate. Similarly, masking layer42 may be used as a mask for etching substrate 20. To simplify furtherdiscussion of masking layer 42, only its use as a mask for an etchingprocess will be discussed in embodiments described below. However, it isrecognized that masking layers in embodiments described herein may beused in a variety of processes as previously described.

For use in an etch process, masking layer 42 may be etched using an etchprocess until portions of substrate 20 are exposed through masking layer42, as depicted in FIG. 23E. That is, portions of the base layer may beetched away. Portions 44 of masking layer 42 may remain on substrate 20for use in inhibiting etching of portions of substrate 20. After etchingof masking layer 42 is complete, substrate 20 may be etched using knownetching processes. Portions of substrate 20 disposed under portions 44of masking layer 42 may remain substantially unetched while the exposedportions of substrate 20 are etched. In this manner, a patterncorresponding to the pattern of template 12 may be transferred tosubstrate 20. The remaining portions 44 of masking layer 42 may beremoved leaving a patterned substrate 20, depicted in FIG. 23F.

FIGS. 24A-24D illustrate an embodiment of an imprint lithography processusing a transfer layer. A transfer layer 18 may be formed upon an uppersurface of substrate 20. Transfer layer 18 may be formed from a materialthat has different etch characteristics than underlying substrate 20and/or masking layer 42 formed from curable liquid 40, depicted in FIGS.23A-23C. That is, each layer (e.g., transfer layer 18, masking layer 42and/or substrate 20) may be etched at least somewhat selectively withrespect to the other layers.

Masking layer 42 is formed on the surface of transfer layer 18 bydepositing curable liquid 40 on the surface of transfer layer 18 andcuring masking layer 42, as depicted in FIGS. 23A-23C. Masking layer 42may be used as a mask for etching transfer layer 18. Masking layer 42 isetched using an etch process until portions of transfer layer 18 areexposed through masking layer 42, as depicted in FIG. 24B. Portions 44of masking layer 42 remain on transfer layer 18 and may be used toinhibit etching of portions of the transfer layer. After etching ofmasking layer 42 is complete, transfer layer 18 may be etched usingknown etching processes. Portions of transfer layer 18 disposed underportions 44 of masking layer 42 may remain substantially unetched whilethe exposed portions of transfer layer 18 are etched. In this manner,the pattern of masking layer 42 is replicated in transfer layer 18.

In FIG. 24C, portions 44 and etched portions of transfer layer 18together form a masking stack 46 that may be used to inhibit etching ofmask portions 44 of underlying substrate 20. Etching of substrate 20 maybe performed using a known etch process (e.g., a plasma etching process,a reactive ion etching process, etc.). As depicted in FIG. 24D, maskingstack 46 may inhibit etching of the underlying portions of substrate 20.Etching of the exposed portions of substrate 20 may be continued until apredetermined depth is reached. An advantage of using a masking stack asa mask for etching of substrate 20 is that the combined stack of layersmay create a high aspect ratio mask (i.e., a mask that has a greaterheight than width). A high aspect ratio masking layer may be desirableduring the etching process to inhibit undercutting of mask portions 44.

The processes depicted in FIGS. 23A-23F and FIGS. 24A-24D are examplesof negative imprint lithography processes. As used herein a “negativeimprint lithography” process generally refers to a process in which thecurable liquid is substantially conformed to the shape of the templatebefore curing. That is, a negative image of the template is formed inthe cured liquid. As depicted in these figures, the non-recessedportions of the template become the recessed portions of the mask layer.The template, therefore, is designed to have a pattern that represents anegative image of the pattern to be imparted to the mask layer.

Positive Imprint Lithography

As used herein a “positive imprint lithography” process generally refersto a process in which the pattern formed in the mask layer is a mirrorimage of the pattern of the template. As will be further describedbelow, the non-recessed portions of the template become the non-recessedportions of the mask layer.

A typical positive imprint lithography process is shown in FIGS.25A-25D. As depicted in FIG. 25A, template 12 is positioned in a spacedrelation to substrate 20 such that a gap is formed between template 12and substrate 20. Surface of template 12 may be treated with a thinsurface treatment layer 13 that lowers template 12 surface energy andassists in separation of template 12 from cured masking layer 42, shownin FIG. 25C.

Curable liquid 40 is disposed on the surface of substrate 20. Template12 is brought into contact with curable liquid 40. As depicted in FIG.25B, curable liquid 40 fills the gap between the lower surface oftemplate 12 and substrate 20. In contrast to a negative imprintlithography process, curable liquid 40 is substantially absent fromregions of substrate 20 approximately below at least a portion of therecesses of template 12. Thus, curable liquid 40 is maintained as adiscontinuous film on substrate 20 that is defined by the location of atleast a portion of the recesses of template 12. After template 12 isproperly positioned, curable liquid 40 is cured to form masking layer 42on substrate 20. Template 12 is removed from masking layer 42, leavingcured masking layer 42 on the surface of substrate 20, as depicted inFIG. 25C. Masking layer 42 has a pattern that is complementary to thepattern of template 12.

Masking layer 42 may be used to inhibit etching of portions of substrate20. After formation of masking layer 42 is complete, substrate 20 may beetched using known etching processes. Portions of substrate 20 disposedunder masking layer 42 may remain substantially unetched while theexposed portions of substrate 20 are etched, as depicted in FIG. 25D. Inthis manner, the pattern of template 12 may be replicated in substrate20. The remaining portions 44 of masking layer 42 may be removed tocreate patterned substrate 20.

FIGS. 26A-26C illustrate an embodiment of a positive imprint lithographyprocess using a transfer layer 18. Transfer layer 18 may be formed uponan upper surface of substrate 20. Transfer layer 18 is formed from amaterial that has different etch characteristics than the underlyingtransfer layer 18 and/or substrate 20. Masking layer 42 is formed on thesurface of transfer layer 18 by depositing a curable liquid on thesurface of transfer layer 18 and curing the masking layer 42, asdepicted in FIGS. 25A-25C.

Masking layer 42 may be used as a mask for etching transfer layer 18.Masking layer 42 may inhibit etching of portions of transfer layer 18.Transfer layer 18 may be etched using known etching processes. Portionsof transfer layer 18, disposed under masking layer 42, may remainsubstantially unetched while the exposed portions of transfer layer 18are etched. In this manner, the pattern of masking layer 42 may bereplicated in transfer layer 18.

In FIG. 26B, masking layer 42 and etched portions of transfer layer 18together form masking stack 46 that may be used to inhibit etching ofportions of the underlying substrate 20. Etching of substrate 20 may beperformed using known etching processes (e.g., a plasma etching process,a reactive ion etching process, etc.). As depicted in FIG. 26C, themasking stack may inhibit etching of the underlying portions ofsubstrate 20. Etching of the exposed portions of substrate 20 may becontinued until a predetermined depth is reached.

Positive/Negative Imprint Lithography

In an embodiment, a process may combine positive and negative imprintlithography. A template for a combined positive and negative imprintlithography process may include recesses suitable for positivelithography and recesses suitable for negative lithography. For example,an embodiment of a template for combined positive and negative imprintlithography is depicted in FIG. 27A. Template 12, as depicted in FIG.27A, includes a lower surface 566, at least one first recess 562, and atleast one second recess 564. First recess 562 is configured to create adiscontinuous portion of curable liquid 40 when template 12 contactscurable liquid 40, depicted in FIG. 27B. A height of first recess (h₂)is substantially greater than a height of second recess (h₁).

A typical combined imprint lithography process is shown in FIGS.27A-27D. As depicted in FIG. 27A, template 12 is positioned in a spacedrelation to substrate 20 such that a gap is formed between template 12and substrate 20. At least the lower surface 566 of template 12 may betreated with a thin surface treatment layer (not shown) that lowerstemplate 12 surface energy and assists in separation of template 12 fromcured masking layer 42. Additionally, surfaces of first recesses 562and/or second recesses 564 may be treated with the thin surfacetreatment layer.

Curable liquid 40 is disposed on the surface of substrate 20. Template12 is brought into contact with curable liquid 40. As depicted in FIG.27B, curable liquid 40 fills the gap between lower surface 566 oftemplate 12 and substrate 20. Curable liquid 40 also fills firstrecesses 562. However, curable liquid 40 is substantially absent fromregions of substrate 20 approximately below second recesses 564. Thus,curable liquid 40 is maintained as a discontinuous film on substrate 20that includes surface topography corresponding to the pattern formed byfirst recesses 562. After template 12 is properly positioned, curableliquid 40 is cured to form masking layer 42 on substrate 20. Template 12is removed from masking layer 42, leaving cured masking layer 42 on thesurface of substrate 20, as depicted in FIG. 27C. Masking layer 42 mayinclude a patterning region 568 that resembles a mask layer formed bynegative imprint lithography. In addition, masking 42 may include achannel region 569 that does not include any masking material.

In one embodiment, masking layer 42 is composed of a material that hasthe same or a similar etch rate as underlying substrate 20. An etchprocess is to be applied to masking layer 42 to remove masking layer 42and substrate 20 at substantially the same etch rate. In this manner themultilayer pattern of template 12 may be transferred to substrate 20, asdepicted in FIG. 27D. This process may also be performed using transferlayer 18 as described in other embodiments.

A combination of positive and negative lithography is also useful forpatterning multiple regions of template 12. For example, substrate 20may include a plurality of regions that require patterning. As depictedin FIG. 27C, template 12 with multiple depth recesses includes twopatterning regions 568 with an intervening “border” region 569. Borderregion 569 inhibits flow of a liquid beyond the patterning area oftemplate 12.

Step and Repeat

As used herein, a “step and repeat” process refers to using a templatesmaller than the substrate to form a plurality of patterned regions onthe substrate. A step and repeat imprint process includes depositing alight curable liquid on a portion of a substrate, aligning a pattern inthe cured liquid to previous patterns on the substrate, impressing atemplate into the liquid, curing the liquid, and separating the templatefrom the cured liquid. Separating the template from the substrate mayleave an image of the topography of the template in the cured liquid.Since the template is smaller than the total surface area of thesubstrate, only a portion of the substrate includes the patterned curedliquid. The “repeat” portion of the process includes depositing a lightcurable liquid on a different portion of the substrate. A patternedtemplate is then aligned with the substrate and contacted with thecurable liquid. The curable liquid is cured using activating light toform a second area of cured liquid. This process may be continuallyrepeated until most of the substrate is patterned. Step and repeatprocesses may be used with positive, negative, or positive/negativeimprint processes. Step and repeat processes may be performed with anyembodiments of equipment described herein.

Step and repeat imprint lithography processes offer a number ofadvantages over other techniques. Step and repeat processes describedherein are based on imprint lithography that uses low viscosity lightcurable liquids and rigid, transparent templates. The templates aretransparent to liquid activating light and alignment mark detectionlight thus offering the potential for layer-to-layer alignment. Forproduction-scale imprint lithography of multi-level devices, it isadvantageous to possess very high-resolution layer-to-layer alignment(e.g., as low as ⅓ of the minimum feature size (“MFS”)).

There are various sources of distortion errors in the making of thetemplates. Step and repeat processes are used so that only a portion ofa substrate is processed during a given step. The size of the fieldprocessed during each step should be small enough to possess patterndistortions of less than ⅓ the MFS. This necessitates step and repeatpatterning in high-resolution imprint lithography. This is also thereason why most optical lithography tools are step and repeat systems.Also, as discussed before, a need for low CD variations and defectinspection/repair favors processing of small fields.

In order to keep process costs low, it is important for lithographyequipment to possess sufficiently high throughput. Throughputrequirements put a stringent limit on the patterning time allowed perfield. Low viscosity liquids that are light curable are attractive froma throughput point of view. These liquids move much faster to properlyfill the gap between the template and the substrate, and the lithographycapability is pattern independent. The resulting low pressure, roomtemperature processing is suitable for high throughput, while retainingthe benefits of layer-to-layer alignment.

While prior inventions have addressed patterning of low viscosity lightcurable liquids, they have not addressed this for a step and repeatprocess. In photolithography, as well as in hot embossing, a film isspin coated and hard baked onto the substrate prior to its patterning.If such an approach is used with low viscosity liquids, there are threemajor problems. Low viscosity liquids are difficult to spin coat sincethey tend to de-wet and cannot retain the form of a continuous film.Also, in a step and repeat process, the liquid undergoes evaporation,thereby causing varying amounts of liquid to be left behind on thesubstrate as the template steps and repeats over the substrate. Finally,a blanket light exposure tends to disperse beyond the specific fieldbeing patterned. This tends to cause partial curing of the subsequentfield, thereby affecting the fluid properties of the liquid prior toimprinting. An approach that dispenses liquid suitable for a singlefield onto the substrate, one field at a time, may solve the above threeproblems. However, it is important to accurately confine the liquid tothat particular field to avoid loss of usable area on the substrate.

In general, lithography is one of many unit processes used in theproduction of devices. The cost of all of these processes, particularlyin multi-layer devices, makes it highly desirable to place patternedregions as close as possible to each other without interfering withsubsequent patterns. This effectively maximizes the usable area andhence the usage of the substrate. Also, imprint lithography may be usedin a “mix-and-match” mode with other kinds of lithography (such asoptical lithography) wherein different levels of the same device aremade from different lithography technologies. It is advantageous to makethe imprint lithography process compatible with other lithographytechniques. A border region separates two adjacent fields on asubstrate. In state-of-the-art optical lithography tools this borderregion may be as small as 50-100 microns. The size of the border istypically limited by the size of the blades used to separate thepatterned regions. This small border is expected to get smaller as theblades that dice the individual chips get thinner. In order toaccomplish this stringent border size requirement, the location of anyexcess liquid that is expelled from the patterned area should be wellconfined and repeatable. As such, the individual components, includingthe template, substrate, liquid and any other materials that affect thephysical properties of the system including, but not limited to, surfaceenergy, interfacial energies, Hamacker constants, Van der Waals' forces,viscosity, density, opacity, etc., are engineered as described herein toproperly accommodate a repeatable process.

Formation of Discontinuous Films

As discussed previously, discontinuous films are formed using anappropriately patterned template. For example, a template with highaspect ratio recesses that define a border region can inhibit the flowof a liquid beyond the border area. The inhibition of the liquid withina border area is influenced by a number of factors. As discussed abovetemplate design plays a role in the confinement of a liquid.Additionally, the process by which the template is contacted with theliquid also influences the confinement of the liquid.

FIGS. 19A-19C depict a cross-sectional view of a process whereindiscontinuous films are formed on a surface. In one embodiment, curableliquid 40 is dispensed onto substrate 20 as a pattern of lines ordroplets, as depicted in FIG. 19A. Curable liquid 40, therefore, doesnot cover an entire area of substrate 20 to be imprinted. As lowersurface 536 of template 12 contacts curable liquid 40, the force oftemplate 12 on curable liquid 40 causes the curable liquid 40 to spreadover the surface of substrate 20, as depicted in FIG. 19B. Generally,the more force that is applied by template 12 to curable liquid 40, thefurther curable liquid 40 will spread over substrate 20. Thus, if asufficient amount of force is applied, curable liquid 40 may be forcedbeyond a perimeter of template 12, as depicted in FIG. 19C. Bycontrolling the forces applied to curable liquid 40 by template 12, theliquid is confined within the predetermined borders of template 12, asdepicted in FIG. 19D.

The amount of force applied to curable liquid 40 is related to theamount of liquid dispensed on substrate 20 and the distance template 12is from the substrate during curing. For a negative imprint lithographyprocess the amount of fluid dispensed onto the substrate should be lessthan or equal to a volume defined by: the volume of liquid required tosubstantially fill the recesses of the patterned template, the area ofthe substrate to be patterned, and the desired thickness of the curedlayer. If the amount of cured liquid exceeds this volume, the liquidwill be displaced from the perimeter of the template when the templateis brought to the appropriate distance from the substrate. For apositive imprint lithography process the amount of liquid dispensed ontothe substrate should be less than the volume defined by: the desiredthickness of the cured layer (i.e., the distance between thenon-recessed portions of the template and the substrate) and the surfacearea of the portion of the substrate to be patterned.

For an imprint lithography process that uses a template that includesone or more borders, the distance between the non-recessed surface ofthe template and the substrate is set between the minimum film thicknessand the maximum film thickness, as previously described. Setting theheight between these values allows the appropriate capillary forces tocontain the liquid within the border-defined areas of the template.Additionally, the thickness of the layer should be approximatelycomparable to the height of the patterned features. If the cured layeris too thick, the features formed in the cured layer may be erodedbefore the features can be transferred to the underlying substrate. Itis therefore desirable to control the volume as described above to allowthe appropriate film thickness to be used.

The force applied by template 12 to curable liquid 40 is also influencedby the rate at which template 12 is brought into contact with curableliquid 40. Generally, the faster template 12 is brought into contact,the more force is applied to curable liquid 40. Thus, some measure ofcontrol of the spread of curable liquid 40 on the surface of substrate12 may be achieved by controlling the rate at which template 12 isbrought into contact with curable liquid 40.

All of these features are considered when positioning the template withrespect to the substrate for an imprint lithography process. Bycontrolling these variables in a predetermined manner, the flow ofliquid may be controlled to stay confined within a predetermine area.

Alignment Techniques

Overlay alignment schemes include measurement of alignment errorsfollowed by compensation of these errors to achieve accurate alignmentof a patterned template and a desired imprint location on a substrate.Correct placement of the template with respect to the substrate isimportant for achieving proper alignment of the patterned layer with anypreviously formed layers on the substrate. Placement error, as usedherein, generally refers to X-Y positioning errors between a templateand substrate (that is, translation along the X- and/or Y-axis).Placement errors, in one embodiment, are determined and corrected for byusing a through-the-template optical device, as depicted in FIG. 14.

FIG. 28 illustrates a schematic diagram of optical system 3820 ofthrough-the-template optical imaging system 3800 (see also FIG. 14).Optical system 3820 is configured to focus two alignment marks fromdifferent planes onto a single focal plane. Optical system 3820 may usethe change of focal length resulting from light with distinctwavelengths to determine the alignment of the template with anunderlying substrate. Optical system 3820 may include optical imagingdevice 3810, an illumination source (not shown), and focusing device3805. Light with distinct wavelengths may be generated either by usingindividual light sources or by using a single broad band light sourceand inserting optical band-pass filters between the imaging plane andthe alignment marks. Depending on the gap between patterned template3700 and substrate 2500, different wavelengths are selected to adjustthe focal lengths. Under each wavelength of light used, each overlaymark may produce two images on the imaging plane, as depicted in FIG.29. A first image 2601, using a specific wavelength of light, is aclearly focused image. A second image 2602, using the same wavelength oflight, is an out-of-focus image. In order to eliminate each out-of-focusimage, several methods may be used.

In a first method, under illumination with a first wavelength of light,two images may be received by optical imaging device 3810. Images aredepicted in FIG. 29 and generally referenced by numeral 2604. Whileimages are depicted as squares, it should be understood that any othershape may be used, including crosses. Image 2602 corresponds to anoverlay alignment mark on the substrate. Image 2601 corresponds to anoverlay alignment mark on the template. When image 2602 is focused,image 2601 is out of focus. In an embodiment, an image processingtechnique may be used to erase geometric data corresponding to pixelsassociated with image 2602. Thus, the out-of-focus image of thesubstrate mark may be eliminated, leaving only image 2601. Using thesame procedure and a second wavelength of light, images 2605 and 2606may be formed on optical imaging device 3810. Te out-of-focus image 2606is then eliminated, leaving only image 2605. The two remaining focusedimages 2601 and 2605 are then combined onto a single imaging plane 2603for making overlay error measurements.

A second method may utilize two coplanar polarizing arrays, as depictedin FIG. 30, and polarized illumination sources. FIG. 30 illustratesoverlay marks 2701 and orthogonally polarizing arrays 2702. Polarizingarrays 2702 are formed on the template surface or placed above thesurface. Under two polarized illumination sources, only focused images2703 (each corresponding to a distinct wavelength and polarization) mayappear on the imaging plane. Thus, out-of-focus images are filtered outby polarizing arrays 2702. An advantage of this method may be that itmay not require an image processing technique to eliminate out-focusedimages.

Moiré pattern-based overlay measurement has been used for opticallithography processes. For imprint lithography processes, where twolayers of Moiré patterns are not on the same plane but still overlappedin the imaging array, acquiring two individual focused images may bedifficult to achieve. However, carefully controlling the gap between thetemplate and substrate within the depth of focus of the opticalmeasurement tool and without direct contact between the template andsubstrate may allow two layers of Moiré patterns to be simultaneouslyacquired with minimal focusing problems. It is believed that otherstandard overlay schemes based on the Moiré patterns may be directlyimplemented to imprint lithography processes.

Another concern with overlay alignment for imprint lithography processesthat use UV curable liquid materials may be the visibility of thealignment marks. For the overlay placement error measurement, twooverlay marks, one on the template and the other on the substrate areused. However, since it is desirable for the template to be transparentto a curing agent, the template overlay marks, in some embodiments, arenot opaque lines. Rather, the template overlay marks are topographicalfeatures of the template surface. In some embodiments, the marks aremade of the same material as the template. In addition, UV curableliquids may have a refractive index that is similar to the refractiveindex of the template materials (e.g., quartz). Therefore, when the UVcurable liquid fills the gap between the template and the substrate,template overlay marks may become very difficult to recognize. If thetemplate overlay marks are made with an opaque material (e.g.,chromium), the UV curable liquid below the overlay marks may not beproperly exposed to the UV light.

In an embodiment, overlay marks are used on the template that are seenby optical imaging system 3800 but are opaque to the curing light (e.g.,UV light). An embodiment of this approach is illustrated in FIG. 31. InFIG. 31, instead of completely opaque lines, overlay marks 3102 on thetemplate may be formed of fine polarizing lines 3101. For example,suitable fine polarizing lines have a width about ½ to ¼ of thewavelength of activating light used as the curing agent. The line widthof polarizing lines 3101 should be small enough so that activating lightpassing between two lines is diffracted sufficiently to cause curing ofall the liquid below the lines. In such an embodiment, the activatinglight may be polarized according to the polarization of overlay marks3102. Polarizing the activating light provides a relatively uniformexposure to all the template regions, including regions having overlaymarks 3102. Light used to locate overlay marks 3102 on the template maybe broadband light or a specific wavelength that may not cure the liquidmaterial. This light need not be polarized. Polarizing lines 3101 aresubstantially opaque to the measuring light, thus making overlay marks3102 visible using established overlay error measuring tools. Finepolarized overlay marks are fabricated on the template using existingtechniques, such as electron beam lithography.

In another embodiment, overlay marks 3102 are formed of a differentmaterial than the template. For example, a material selected to form thetemplate overlay marks 3102 may be substantially opaque to visiblelight, but transparent to activating light used as the curing agent(e.g., UV light). For example, SiO_(x), where X is less than 2, may beused as such a material. In particular, structures formed of SiO_(x),where X is about 1.5, are substantially opaque to visible light, buttransparent to UV curing light.

Off-Axis Alignment

In one embodiment, alignment of one or more template alignment marks maybe accomplished using an off-axis alignment process. As described above,a system may include off-axis optical imaging devices coupled to theimprint head and the motion stage. While the following description isdirected to systems that have the substrate mounted to a motion stage,it should be understood that the process may be readily modified forsystems that have an imprint head mounted to a motion stage.Additionally, it should be understood that the following descriptionassumes that magnification errors have been corrected prior toperforming an alignment process. Magnification errors occur whenmaterials expand or contract due to changes in temperature. Techniquesfor correcting magnification errors are described in U.S. Ser. No.09/907,512 filed Jul. 16, 2001 entitled “High-Resolution OverlayAlignment Methods and Systems for Imprint Lithography,” which isincorporated herein by reference. Also, magnification corrections thatare different in two orthogonal directions in the plane of the patteringareas of the template may also be required before aligning.

FIGS. 46A-46D depict schematic views of a system for off-axis alignmentof a template with a substrate. Imprint head 3100 includes a template3700 and an off-axis imaging device 3840. Substrate 4600 is mounted to asubstrate chuck 3610 which is coupled to a motion stage 3620. Motionstage 3620 is configured to control motion of the substrate 4600 in adirection substantially parallel to the template 3700. Template opticalimaging system 3850 is coupled to motion stage 3620 such that thetemplate optical imaging system 3850 will move with the motion stage3620. The system also includes a system alignment target 4630. Systemalignment target 4630 is coupled to a fixed portion of the system inoptical alignment with template optical imaging system 3850. Systemalignment target 4630 may be coupled to the body of an imprintlithography system or a non-moving optical imaging system (e.g.,template optical imaging system 3840). System alignment target 4630 isused as a fixed reference point for alignment measurements.

Template 3700 and substrate 4600 include at least one, preferably twoalignment marks, as shown in FIG. 46A. During an imprinting process,alignment marks on the template 3700 are aligned with correspondingalignment marks on the substrate 4600 prior to curing a liquid disposedon the substrate 4600. In one embodiment, alignment may be performed byusing off-axis optical imaging devices. FIG. 46A depicts the system inan initialized state. In this initial state the template alignment marksare not aligned with the substrate alignment marks. The opticalalignment systems 3840 and 3850, however, are aligned with systemalignment target 4630. Thus, the starting position of each motion withrespect to a fixed point in the system is known.

To perform alignment of the template 3700 and substrate 4600 thepositions of the alignment marks with respect to the system alignmenttarget 4630 are determined. To determine the positions of the templatealignment marks with respect to the system alignment target 4630, motionstage 3620 is moved until a system alignment target 4630 is in the fieldof view of optical imaging device 3850, shown in FIG. 46B. The movementof the motion stage 3620 required to find the alignment mark (in an X-Yplane) is used to determine the position of the template alignment marksrelative to the system alignment target 4630. The position of thesubstrate alignment targets may be determined by moving the substrate4600 with motion stage 3620 until a substrate alignment mark is in thefield of view of the off-axis optical imaging system 3840, as depictedin FIG. 46C. The movement of the motion stage 3620 required to find thealignment mark (in an X-Y plane) is used to determine the position ofthe template alignment marks relative to the system alignment target4630. In an embodiment, the motion stage 3620 may be brought back to theinitial positions (e.g., as depicted in FIG. 46A) prior to determiningthe position of the substrate alignment marks.

Once the position of the substrate and template alignment marks isdetermined, alignment is achieved by moving the substrate to theappropriate position. FIG. 46D depicts the final aligned state of thetemplate and substrate.

Theta Alignment

To properly align a template with a field on a substrate, the positionof the substrate with respect to the template is selected to allowalignment of alignment marks on the template and substrate. Typically,two or more alignment marks are formed on a template. Correspondingalignment marks are also formed on the substrate. When the alignmentmarks on the template are all properly aligned with the alignment markson the substrate, the imprinting process is performed.

In some embodiments, the template may be rotated about the Z-axis withrespect to the substrate. In such embodiments, it may not be possible toalign multiple alignment marks on a template with correspondingalignment marks on the substrate by simple X-Y motion of the substrate.To properly align the template with the selected field on a substrate,the substrate (or template) is rotated about the Z-axis. This rotationalcorrection is herein referred to as a “theta alignment.”

FIG. 47A depicts an overhead view of a template 4710 positioned over asubstrate 4720. Template 4710 includes at least two alignment marks andsubstrate 4720 includes at least two corresponding alignment marks. Whenproperly aligned, all of the template alignment marks should align withall of the corresponding substrate alignment marks.

Initial alignment is conducted by moving the substrate 4720 (or thetemplate 4710) to a position such that at least one of the alignmentmarks on template 4710 is aligned with at least one of the alignmentmarks on substrate 4720, as depicted in FIG. 47B. In the absence of anytheta alignment error (and magnification errors), the other alignmentmarks should match up without any further movement of substrate 4720. Asdepicted in FIG. 47B, however, theta alignment errors will cause theother alignment marks on template 4710 and substrate 4720 to bemisaligned. Before further imprinting is performed, theta errorcorrection is performed.

Theta error correction is accomplished by rotating substrate 4720 (ortemplate 4710) about the Z-axis (i.e., the axis extending out of thepage perpendicular to the X and Y axis of the page). Rotation ofsubstrate 4720 will allow alignment of all the template and substratealignment marks, as depicted in FIG. 47C.

Theta error may be detected (and corrected for) using either off-axis orthrough-the-template alignment procedures. As described herein, off-axisalignment techniques allow the position of various alignment marks to bedetermined with respect to a fixed references point (e.g., the systemalignment target). FIG. 47D depicts an overhead view of a template 4710positioned over a substrate 4720. Template 4710 includes at least twoalignment marks and substrate 4720 includes at least two correspondingalignment marks.

Initially, using off-axis imaging devices, the position of the twotemplate alignment marks and the two substrate alignment marks isdetermined relative to the system alignment target 4730. The systemalignment target 4730 defines the vertex of an X reference axis and a Yreference axis. The direction of the X reference axis and Y referenceaxis with respect to system alignment target 4730 is determined by thedirection of X-motion and Y-motion of motion stage 3620, shown in FIG.46D, respectively. The positions of the template alignment marks areused to determine the angle of a line 4740 that passes through thetemplate alignment marks with respect to the X and Y reference axis. Thepositions of the substrate alignment marks are used to determine theangle of a line 4750 that passes through the substrate alignment marks,with respect to the X and Y reference axis. The angles of lines 4740 and4750 may be determined using standard geometric functions. Thedifference in determined angle of 4740 and 4750 with respect to the Xand Y reference axis represents the theta alignment error.

After determining the theta error, the motion stage is rotated to be theappropriate amount to correct for this error. Once corrected, the angleof line 4740, drawn through the template alignment marks, and line 4750,drawn through the substrate alignment marks, with respect to the X and Yreference axis, should be substantially the same. After theta correctionis completed, the template and substrate alignment marks are broughtinto final alignment by X-Y movement of the motion stage. Imprintingprocesses are afterward performed with the properly aligned template andsubstrate.

In another embodiment, through-the-template alignment methods may beused to correct for theta errors and align the template with thesubstrate. Through-the-template alignment techniques are conducted byobserving the alignment of a template alignment mark with respect to acorresponding substrate alignment mark by observing both marks. Asdescribed herein, this may be accomplished using an optical system thatallows viewing the template and substrate alignment marks through thetemplate.

FIG. 47E depicts an overhead view of a template 4710 positioned over asubstrate 4720. Template 4710 includes at least two alignment marks andsubstrate 4720 includes at least two corresponding alignment marks.

Initially, using a through-the-template optical imaging device, themotion stage is moved such that a first template alignment mark isaligned with a first substrate alignment mark, as depicted in FIG. 47E.The positions of the second template alignment mark and the secondsubstrate alignment mark are determined by moving the optical imagingdevice across the template 4710 until the alignment marks are found.Once the location of the alignment marks are found, imaginary lines 4740(between the template alignment marks) and 4750 (between the substratealignment marks) are calculated and used to determine the theta anglebetween the two lines. This angle represents the theta error.

In one embodiment, the position of the second template and substratealignment marks is determined by the movements of the motion stage.Initially the first template and substrate alignment marks are alignedas depicted in FIG. 47E. The optical imaging device is moved to find thesecond template alignment mark. After finding this mark, the motionstage is moved, while the optical imaging device is maintained in thesame position, until the first template alignment mark is brought backinto the field of view of the optical imaging device. The movement ofthe motion stage is monitored and this movement is used to calculate theposition of the second template alignment mark with respect to the firsttemplate alignment mark. The position of the second template alignmentmark with respect to the first template alignment mark is determinedbased on an X-Y reference plane defined by the direction of X-motion andY-motion of the motion stage. In a similar manner, the position of thesecond substrate alignment mark is determined with respect to the firstsubstrate alignment mark.

After determining the theta error, motion stage 3620, shown in FIG. 46D,is rotated by the appropriate amount to correct for this error. Aftertheta correction is completed, the template and substrate alignmentmarks are brought into final alignment by X-Y movement of the motionstage. Imprinting processes are afterward performed with the properlyaligned template and substrate.

In another embodiment, both off-axis and through-the-template alignmentmay be used together to align the template with the substrate. In thisembodiment, off-axis methods may be used to perform a first alignment,while through-the-template alignment may be used to refine the alignmentof the template with the substrate. Both theta correction and X-Ycorrections are performed using both techniques.

The above-described theta correction alignment processes may be used forstep and repeat processes. Step and repeat alignment may be conductedeither by global or field-by-field alignment. For global alignment, twoor more fields of a substrate will include at least two alignment marks.Off-axis or through-the-template alignment is conducted at two or morefields and the theta alignment error and X-Y alignment error at eachfield is determined. Optionally, alignment at each field may beaccompanied by an imprinting step. The theta alignment errors and X-Yalignment errors at each field are then averaged to determine an“average alignment error.” The average alignment error is used todetermine the correction necessary to apply at any field on thesubstrate.

The average alignment error is then used in a step and repeat process.In the step and repeat process, each field's position is predeterminedand stored in a database of the lithography system. During imprinting,the motion stage is moved such that the template is oriented over thedesired position of the substrate based on the coordinates stored in thedatabase. The template and substrate are then subjected to an alignmentcorrection based on the average alignment error. Activating lightcurable liquid may be placed on the substrate prior to or afteralignment correction. Activating light is applied to cure the activatinglight curable liquid and the template separated from the cured liquid.The motion stage is moved to orient the template over another portion ofthe substrate and the process is repeated.

Alternatively, a field-by-field alignment process may be used. Duringimprinting, the motion stage is moved such that the template is orientedover the desired field of the substrate based on the coordinates storedin the database. Each field of the substrate includes two or morealignment marks that correspond to alignment marks on the template. Thetemplate alignment marks are then aligned with the substrate alignmentmarks at the specific field being imprinted using wither off-axis,through-the-template, or a combination of these alignment techniques.Activating light curable liquid may be placed on the substrate prior toor after alignment. Activating light is applied to cure the activatinglight curable liquid and the template separated from the cured liquid.The motion stage is moved to orient the template over another field ofthe substrate and the template. Alignment is conducted with eachindividual field of the substrate.

Scatterometry Alignment Techniques

In one embodiment, alignment may be performed using scatterometry.Scatterometry is a technique used to measure the properties of lightscattered off of a surface. For alignment of a template with asubstrate, scatterometry uses diffraction gratings on the substrate andthe template. In imprint lithography an alignment mark on the templateand an alignment mark on the substrate can be separated from each otherby less than 200 nm. The alignment system may, therefore, look at bothalignment marks simultaneously. Generally, incident light on thealignment marks will be scattered from the alignment marks in apredictable manner depending on the orientation of the alignment markswith respect to each other. In one embodiment, the scattering of lightwhen the alignment marks are aligned is calculated to generate ascattering profile. During use, alignment is achieved by moving eitherthe substrate or the template until the scattered light profile from thealignment marks substantially matches the predetermined scatteringprofile.

During patterning of a substrate using imprint lithography, thepatterned template is positioned over a predetermined portion of thesubstrate. Typically, the portion of the substrate which is beingimprinted will have structures previously formed. Prior to imprinting,the patterned template needs to be aligned with the previously formedstructures on the substrate. For sub-100 nm imprint lithography,alignment of a template with features on a substrate should be possiblewith an accuracy of less than about 25 nm, for some embodiments, lessthan about 10 nm. Alignment of the template with a substrate istypically achieved by the use of alignment marks. Matching alignmentmarks are formed in the substrate and the template and positioned in apredetermined position. When the alignment marks are properly aligned,the template is properly aligned with the substrate and the imprintprocess is performed.

Generally, alignment may be performed using high-power microscopes. Suchmicroscopes collect images of the alignment marks. The collected imagesare analyzed by a user and the user may alter the position of thetemplate with respect to the substrate to bring the images intoalignment and, therefore, bring the template into alignment with theunderlying substrate. High-power microscopes that can achieve alignmentaccuracies of less than 10 nm are very expensive and may be difficult toimplement within an imprint lithography system.

Scatterometry offers a technique for collecting image data withouthaving to image the features. In general, the scatterometry toolincludes optical hardware, such as an ellipsometer or reflectometer, anda data processing unit loaded with a scatterometry software applicationfor processing data collected by the optical hardware. The scatterometrytool generally includes an analyzing light source and a detector whichare positionable proximate to alignment marks on the substrate andtemplate. The light source may illuminate at least a portion of adiffraction grating structure of an alignment mark. The detector takesoptical measurements, such as intensity or phase, of the reflectedlight. The data processing unit receives the optical measurements fromthe detector and processes the data to determine the scattering profileof light off of the diffraction grating.

The scatterometry tool may use monochromatic light, white light, or someother wavelength or combinations of wavelengths, depending on thespecific implementation. The angle of incidence of the light may alsovary, depending on the specific implementation. The light analyzed bythe scatterometry tool typically includes a reflected component (i.e.,incident angle equals reflected angle) and a scattered component (i.e.,incident angle does not equal the reflected angle). For purposes ofdiscussion hereinafter, the term “reflected” light is meant to encompassboth components.

When the alignment mark on a template is aligned with an alignment markon a substrate, light is reflected off of the surfaces in a manner thatcan be characterized by a reflection profile. Misalignment of thetemplate alignment mark with the substrate alignment mark causes changesin the reflection profile (e.g., intensity, phase, polarization, etc.)measured by the scatterometry tool as compared to the light reflectionprofile that would be present when the marks are aligned. During use,the scatterometry tool measures reflection profiles for the alignmentmarks. A difference in the reflection profiles measured for thealignment marks during use indicates a misalignment of the template withthe substrate.

A data processing unit of the scatterometry tool compares the measuredreflection profile to the reference reflection profile library. Thedifferences are between the measured reflection profile and thereference reflection profiles are used to determine the alignment of thetemplate alignment mark with the substrate alignment mark.Alternatively, when the two gratings are aligned, the scattering patternfrom a normal incident beam should be symmetrical, i.e., the + and − 1orders should be the same, or any order (including zero) from twoopposing low angle incident beams should be the same. The symmetricalsignals from multiple wavelengths would be subtracted, and thedifferences summed to measure alignment and the wafer or template movedto minimize the sum.

Scatterometry offers advantages over optical imaging processes. Theoptical requirements of a scatterometry tool are much less than for anoptical imaging system. Additionally, the scatterometry allowsadditional optical information (such as light phase and polarization) tobe collected that can not be collected using an optical imaging devicesuch as a microscope.

An illustrative alignment mark is depicted in FIG. 48A. Alignment mark4800 includes a plurality of trenches 4810 formed in substrate 4820(e.g., the template or the substrate upon which the imprinted layer isbeing formed) that together define diffraction gratings (e.g., 4825 and4827). Alignment mark 4800 is shown in cross-section in FIG. 48B.Typically, a diffraction grating may be formed by etching a plurality ofgrooves in a substrate. The grooves have substantially the same widthand depth and are evenly spaced. To allow alignment along the X and Yaxis, at least two sets of diffraction gratings are used. As depicted inFIG. 48A, a first group of trenches 4810 a define a diffraction grating4825 for alignment along a first axis (e.g., the X-axis). A second groupof trenches 4810 b define a diffraction grating 4827 for alignment alonga second axis (e.g., the Y-axis).

An alternate embodiment of an alignment mark is depicted in FIG. 48C. Atleast four sets of diffraction gratings are used for alignment of atemplate with a substrate. Diffraction gratings are formed from aplurality of trenches 4810 etched into the substrate 4820 as shown inFIGS. 48A and 48B. Two of the diffraction gratings, 4830 and 4840 areused for a coarse alignment of the template with the substrate. Thecoarse alignment gratings are formed from a plurality of trenches thathave substantially the same width and depth and are evenly spaced. Thecoarse alignment diffraction grating trenches may be spaced at distancesof between about 1 μm to about 3 μm. Diffraction gratings having aspacing in this range may be used to align a template with a substratewith an accuracy of up to about 100 nm. Diffraction grating 4830 is usedfor alignment along a first axis (e.g., the X-axis). Diffraction grating4840 is used for alignment along a second axis (e.g., the Y-axis).

When imprinting structures having a feature size of less than about 100nm onto a surface, such accuracy is not sufficient to allow properorientation of different pattering layers. Additional diffractiongrating structures, 4850 and 4860 may be used for a fine alignment. Thefine diffraction gratings 4850 and 4860 are formed from a plurality oftrenches that have substantially the same width and depth and are evenlyspaced. The fine alignment diffraction grating trenches may be spaced atdistances of between about 100 nm to about 1000 nm. Diffraction gratingshaving a spacing in this range may be used to align a template with asubstrate with an accuracy of up to about 5 nm. Diffraction grating 4850is used for alignment along a first axis (e.g., the X-axis). Diffractiongrating 4860 is used for alignment along a second axis (e.g., theY-axis).

FIG. 49 depicts a configuration of a scatterometry tool 4900 used todetermine alignment between a template alignment mark 4910 and asubstrate alignment mark 4920. Scatterometry tool 4900 produces anincident light beam 4930 which is directed to the alignment marks 4910and 4920, as depicted. Incident light beam 4930 is directed in adirection that is substantially normal to the plane of the template (orsubstrate). Incident light beam 4930 may be produced from a white lightsource or any other source of light that is capable of producingmultiple wavelengths of light. The light source used to produce thelight may be disposed in the imprint head of an imprint system asdescribed herein. Alternatively, a light source may be coupled to a bodyoutside of the imprint head and an optical system may be used to conductlight to the template.

When light from the light source contacts the alignment marks 4910 and4920, the light is scattered as depicted in FIG. 49. As is known in theart, scattering of light occurs to produce maximum light intensities atdifferent angles. The angles at which the different light maxima areproduced correspond to different diffraction orders. Typically,pluralities of orders are produced when light is reflected off of adiffraction grating. The zero order, as used herein, refers to lightthat is reflected back to the light source along the same optical pathas the incident light. As depicted in FIG. 49, light reflected back tolight source along incident light beam 4930 would be the zero order.First, order light is reflected off the diffraction gratings along anangle that differs from the angle of incidence. As depicted in FIG. 49,light beams 4942 and 4944 represent light produced along the positivefirst order (i.e., order +1) and light beams 4952 and 4954 representlight produced along the negative first order (i.e., order −1). Whilethe +1 and −1 orders are depicted, it should be understood that otherorders of light (e.g., N order, where n is greater than zero) may beused.

During use, light reflected from the substrate (and thethrough-the-template) is collected by detector 4960. Detector 4960, inone embodiment, is an array detector capable of simultaneously measuringlight properties at a plurality of positions. When light is scatteredfrom a diffraction grating, individual wavelengths of light arescattered differently. Generally, all wavelengths will be scatteredalong one of the diffraction orders; however, the different wavelengthof light will be scattered at slightly different angles. FIG. 49 showshow two different wavelengths of light are reflected along the +1 and −1orders. It should be noted that the difference in scattering angle hasbeen exaggerated for the purposes of this discussion. Turning to the +1order, light beam 4942 represents red light while light beam 4944represents blue light. For the −1 order, light beam 4952 represents redlight while light beam 4954 represents blue light. As depicted, the redlight beams 4942 and 4944 and blue light beams 4944 and 4954 contactdifferent portions of the detector 4960. Detector 4960 includes an arrayof light detection elements. The size and location of the lightdetection elements are such to allow analysis of the differentwavelengths of light. As depicted in FIG. 49, red light 4942 hits adifferent light detection element than blue light 4944. Thus thescatterometry tool 4900 may simultaneously measure light properties atmultiple wavelengths.

An advantage of measuring scattering at multiple wavelengths of light isthat phase errors may be averaged out. Phase errors are caused byirregularities in the etching of the trenches that form the diffractiongrating. For example, if the walls are non-parallel or the bottom of thetrench is angled, light scattering may not follow the predicted model.Such errors tend to vary depending on the wavelength of light used foranalysis. For example, processing errors in forming the trench may causemore deviation for red light than for blue light. By taking readings atmultiple wavelengths, the singles may be averaged to create a moreaccurate guide for alignment.

In an alternate embodiment, depicted in FIG. 50, the reflected lightfrom the alignment marks may be scattered, as described above for FIG.49. Instead of relying on the resolution of the detector to capture thedifferent wavelengths of light, the reflected light may be split usingan optical element 5070. As described above, a template alignment mark5010 and a substrate alignment mark 5020 are illuminated with incidentlight 5030. Incident light 5030 is directed in a direction that isnormal to the plane defined by the template. Light reflected from thediffraction gratings of the alignment marks 5010 and 5020 is analyzedalong the +1 order (5040) and −1 order (5050). In this embodiment, anoptical element 5070, is placed in the optical path between thesubstrate and the detector 5060. Optical element 5070 is configured todiffract light at different angles based on the wavelength of light.Optical element 5070 may be, for example, a diffraction grating (e.g.,as part of a spectrophotometer) or a prism. Both prisms and diffractiongratings will diffract light at different angles based on the wavelengthof the light. As depicted in FIG. 50, red light is diffracted at adifferent angle than the blue light. While depicted as a single elementin FIG. 50, it should be understood that optical element 5070 may becomposed of two individual elements. Additionally, while optical element5070 and detector 5060 are depicted as individual elements, it should beunderstood that the elements may be incorporated into a single device(e.g., a spectrophotometer).

Alternatively, optical element 5070 may be a lens. When optical element5070 is a lens, diffraction occurs when the light passes through thelens. The extent of diffraction is based, in part, on the index ofrefraction of the lens material. The extent of diffraction is also basedon the wavelength of the light. Different wavelengths of light will bediffracted at different angles. This causes what is known as “chromaticaberration.” Chromatic aberration may be taken advantage of to enhancethe separation of light into different wavelengths. In some embodiments,two lenses may be used, one for each order of light.

Scatterometry as described above may be used for an imprint lithographyprocess. In an embodiment, a predetermined amount of an activating lightcurable liquid is placed on a portion of a substrate to be imprinted. Apatterned template is positioned proximate to the substrate. Generally,the template is separated from the substrate by a distance of less thanabout 200 nm. To ensure proper alignment of the patterned template withpreviously formed structures on the substrate, a template alignmenttarget is aligned with a substrate alignment target. The templatealignment target includes a diffraction grating to allow a scatteringtechnique to be used for alignment. Initial alignment of the templatealignment mark with the substrate alignment mark is accomplished usingoptical imaging of the marks. The marks are aligned using patternrecognition software. Such alignment may be used to achieve an alignmentaccuracy within about 1 micron.

Scatterometry is used for the next iteration of alignment. In oneembodiment, an alignment mark may include a coarse alignment diffractiongrating and a fine alignment diffraction grating, such as the alignmentmark 4800 depicted in FIG. 48C. A coarse alignment of the alignmentmarks may be performed using the coarse alignment diffraction gratings.A fine alignment of the alignment marks may be performed using the finealignment diffraction gratings. All alignment measurements may beperformed with the activating light curable liquid disposed between thetemplate and the substrate. As described herein, an optical imagingdevice may be used to perform the initial alignment. Prior to performingscatterometry, the optical imaging device may be moved out of theoptical path between a light source and the template. Alternatively,light from the light source may be directed in such a manner that theoptical imaging device does not lie in the optical path between thelight source and the template.

In an embodiment, light may be directed to the template and substratealignment marks normal to the plane defined by the template. Lightscattering along the +1 and −1 orders may be analyzed at a plurality ofwavelengths. Intensity levels of light scattered at the +1 order arecompared to light intensity levels of light scattered at the −1 order.If the template alignment mark and the substrate alignment mark arealigned, the intensities should be substantially identical at any givenwavelength. Differences in the intensity of light between the +1 and −1orders indicate that the alignment marks may be misaligned. Comparisonof the degree of misalignment at a plurality of wavelength is used toproduce an “average” misalignment of the alignment marks.

The average misalignment of the template and substrate alignment marksmay be used to determine a correction needed in the position of thetemplate with respect to the substrate to properly align the alignmentmarks. In one embodiment, the substrate is disposed on a substratemotion stage. Alignment may be achieved by moving the substrate in anappropriate manner as determined by the average misalignment calculatedusing scatterometry. After the template and substrate are properlyaligned, curing of the liquid followed by separation of the templatefrom the cured liquid may be performed.

FIG. 51 depicts an alternate configuration of a scatterometry tool 5100used to determine alignment between a template alignment mark 5110 and asubstrate alignment mark 5120. Scatterometry tool 5100 uses measurementsof two zero order reflections off the substrate to determine thealignment of the alignment marks 5110 and 5120. Two light sourcesproduce two incident light beams 5130 and 5135 which are directed to thealignment marks 5110 and 5120, as depicted. Incident light beams 5130and 5135 are directed in a direction that is substantially non-normal tothe plane of the template (or substrate). Incident light beams 5130 and5135 may be produced from a white light source or any other source oflight that is capable of producing multiple wavelengths of light.Incident light beams 5130 and 5135 are passed through beam splitters5192 and 5194, respectively.

When light from the light source contacts the alignment marks 5110 and5120, the light is scattered as described above. Zero order light is thelight that is reflected back to the light source along the same opticalpath as the incident light. Light reflected back toward the light isfurther reflected by beam splitters 5192 and 5194 toward detectors 5160and 5162. Detectors 5160 and 5162, in one embodiment, are arraydetectors capable of simultaneously measuring light properties at aplurality of positions. When light is scattered from a diffractiongrating, individual wavelengths of light are scattered differently.Generally, all wavelengths will be scattered along one of thediffraction orders, however, the different wavelength of light will bescattered at slightly different angles, as discussed before. It shouldbe noted that the difference in scattering angle has been exaggeratedfor the purposes of this discussion. For incident light beam 5130, lightbeam 5142 represents red light while light beam 5144 represents bluelight. For incident light beam 5135, light beam 5152 represents redlight while light beam 5154 represents blue light. As depicted, the redlight beams 5142 and 5152 and blue light beams 5144 and 5154 contactdifferent portions of detectors 5160 and 5162. Detector 5160 includes anarray of light detection elements. The size and location of the lightdetection elements are such to allow analysis of the differentwavelengths of light. As depicted in FIG. 51, red light 5142 hits adifferent light detection element than blue light 5144. Thus thescatterometry tool 5100 may simultaneously measure light properties atmultiple wavelengths. The use of an array detector has the additionaladvantage that any small changes in the orientation of the wafer ortemplate or any other mechanical changes that cause changes in thepositions of the order peaks can be detected and the intensities can becorrectly measured.

Scatterometry tool 5100 depicted in FIG. 51 takes advantage of thestrongest reflected signals (i.e., the zero order signals) foralignment. Generally, the differences in the alignment of the gratingsis not very great along the zero order when the incident light is normalto the gratings. By using non-normal angles of incidence it is believedthat that the zero order shows more sensitivity to misalignment of thegratings. Additionally, the optical path for the scatterometry tool 5100allows the placement of an optical imaging device 5180 in the center ofthe scatterometry tool 5100. As described herein, optical imaging device5180 may be used for coarse alignment of the template and substratealignment marks 5110 and 5120. During alignment of the template andsubstrate using scatterometry tool 5100, movement of the optical imagingdevice may not be required.

In an alternate embodiment, depicted in FIG. 52, the reflected lightfrom the alignment marks 5210 and 5220 may be scattered as describedabove for FIG. 51. Instead of relying on the resolution of the detectorto capture the different wavelengths of light, the reflected light maybe split using optical elements 5272 and 5274. As described above,template alignment mark 5210 and substrate alignment mark 5220 areilluminated with two beams of incident light 5230 and 5235. Incidentlight beams 5230 and 5235 are directed in a direction that is non-normalto the plane defined by the template. Light reflected from thediffraction gratings of alignment marks 5210 and 5220 is analyzed alongthe zero order by reflecting the light with beam splitters 5292 and5294. In this embodiment, optical elements 5272 and 5274 are placed inthe optical path between the substrate and detectors 5260 and 5262.Optical elements 5272 and 5274 are configured to diffract light atdifferent angles based on the wavelength of light. Optical elements 5272and 5274 may be, for example, a diffraction grating (e.g., as part of aspectrophotometer) or a prism. Alternatively, optical elements 5272 and5274 may be a lens that exhibits chromatic aberrations.

In an alternate embodiment, depicted in FIG. 53, the reflected lightfrom the alignment marks may be scattered as described above for FIG.51. Instead of relying on the resolution of the detector to capture thedifferent wavelengths of light, the reflected light may be split usingoptical elements 5372 and 5374. Light that is reflected off of thealignment marks is directed by beam splitters 5392 and 5394 into fiberoptic cables 5376 and 5378, respectively. The fiber optic cables 5376and 5378 carry the light from the imprint system to optical elements5372 and 5374. Optical elements 5372 and 5374 are configured to diffractlight at different angles based on the wavelength of light. Opticalelements 5372 and 5374 may be, for example, a diffraction grating (e.g.,as part of a spectrophotometer) or a prism. Alternatively, opticalelements 5372 and 5374 may be a lens that exhibits chromaticaberrations. An advantage of such an embodiment is that a portion of theoptical system may be isolated from the imprint system. This allows theimprint system size to be kept at a minimal.

An alternate embodiment of a configuration of a scatterometry tool 5400used to determine alignment between a template alignment mark 5410 and asubstrate alignment mark 5420 is depicted in FIG. 54. Two light sourcesproduce two incident light beams 5430 and 5435 which are directed to thealignment marks 5410 and 5420, as depicted. Incident light beams 5430and 5435 are directed in a direction that is substantially non-normal tothe plane of the template (or substrate). Incident light beams 5430 and5435 may be produced from a white light source or any other source oflight that is capable of producing multiple wavelengths of light.Incident light beams 5430 and 5435 are passed through beam splitters5492 and 5494, respectively.

When light from the light source contacts the alignment marks 5410 and5420, the light is scattered as depicted in FIG. 54. As depicted in FIG.54, light reflected back to light source along incident light beam 5430and incident light beam 5435 would be the zero order. First order lightis reflected off the diffraction gratings along an angle that differsfrom the angle of incidence. As depicted in FIG. 54, light rays 5440represent light produced along the +1 order of incident light beam 5430.Light rays 5450 represent the +1 order of incident light beam 5440. −1order beams are not depicted. While the +1 orders are depicted, itshould be understood that other orders of light (e.g., N order, where nis greater than zero) may be used.

Light that is reflected off of the alignment marks 5410 and 5420 isdirected by beam splitters 5492 and 5494 into fiber optic cables 5476and 5478, respectively. The fiber optic cables 5476 and 5478 carry thelight from the imprint system to optical elements 5472 and 5474. Opticalelements 5472 and 5474 are configured to diffract light at differentangles based on the wavelength of light. Optical elements 5472 and 5474may be, for example, a diffraction grating (e.g., as part of aspectrophotometer) or a prism. Alternatively, optical elements 5472 and5474 may be a lens that exhibits chromatic aberrations.

Beam splitters 5492 and 5494 will allow a portion of the reflected lightto pass through the beam splitter. The portion of the light that passesthrough the beam splitters 5492 and 5494 is analyzed using lightdetectors 5462 and 5464. Light detectors 5462 and 5464 are used todetermine the total intensity of all light passing through beamsplitters 5492 and 5494. Data concerning the total intensity of lightmay be used to determine the alignment of the template and substratealignment marks 5410 and 5420. In an embodiment, the alignment isdetermined as an average of the error measurements determined by thespectrophotometric analysis of the n order (e.g. +1 order) reflectedlight and the light intensity measurements.

It should be understood that any of the above described embodiments maybe combined for different configurations. Furthermore, it should beunderstood that the light properties used to determine the alignment ofthe template and substrate marks include intensity of light andpolarization of light.

Liquid Dispensing Patterns

In all embodiments of an imprint lithography process, a liquid isdispensed onto a substrate. While the following description is directedto dispensing liquids on substrate, it should be understood that thesame liquid dispensing techniques are also used when dispensing liquidsonto a template. Liquid dispensing is a carefully controlled process. Ingeneral, liquid dispensing is controlled such that a predeterminedamount of liquid is dispensed in the proper location on the substrate.Additionally, the volume of liquid is also controlled. The combinationof the proper volume of liquid and the proper location of the liquid iscontrolled by using the liquid dispensing systems described herein. Stepand repeat processes, in particular, use a combination of liquid volumecontrol and liquid placement to confine patterning to a specified field.

A variety of liquid dispensing patterns are used. Patterns may be in theform of continuous lines or patterns of droplets of liquid. In someembodiments, relative motion between a displacement based liquiddispenser tip and an imprinting member is used to form a pattern withsubstantially continuous lines on a portion of the imprinting member.Balancing rates of dispensing and relative motion are used to controlthe size of the cross-section of the line and the shape of the line.During the dispensing process, the dispenser tips are fixed near (e.g.,on the order of tens of microns) to the substrate. Two examples ofcontinuous patterns are depicted in FIGS. 32A and 32B. The patterndepicted in FIGS. 32A and 32B is a sinusoidal pattern; however, otherpatterns are possible. As depicted in FIGS. 32A and 32B, a continuousline pattern may be drawn using either a single dispenser tip 2401 ormultiple dispenser tips 2402. Alternately, a pattern of droplets may beused, as depicted in FIG. 32C. In one embodiment, a pattern of dropletsthat has a central droplet with a greater volume than surroundingdroplets is used. When the template contacts the droplets, the liquidspreads to fill the patterning area of the template as depicted in FIG.32C.

Dispensing rate, v_(d), and relative lateral velocity of an imprintingmember, v_(s), may be related as follows:v _(d) =V _(d) /t _(d) (dispensing volume/dispensing period),  (1)v _(s) =L/t _(d) (line length/dispensing period),  (2)v _(d) =aL (where, ‘a’ is the cross section area of line pattern),  (3)

Therefore,v _(d) =av _(s).  (4)

The width of the initial line pattern may normally depend on the tipsize of a dispenser. The dispenser tip may be fixed. In an embodiment, aliquid dispensing controller is used to control the volume of liquiddispensed (V_(d)) and the time taken to dispense the liquid (t_(d)). IfV_(d) and t_(d) are fixed, increasing the length of the line leads tolower height of the cross-section of the line patterned. Increasingpattern length may be achieved by increasing the spatial frequency ofthe periodic patterns. Lower height of the pattern may lead to adecrease in the amount of liquid to be displaced during imprintprocesses. By using multiple tips connected to the same dispensing line,line patterns with long lengths may be formed faster as compared to thecase of a single dispenser tip. Alternatively, a plurality of closelyspaced drops is used to form a line with an accurate volume.

Separation of Template

After curing of the liquid is completed, the template is separated fromthe cured liquid. Since the template and substrate are almost perfectlyparallel, the assembly of the template, imprinted layer, and substrateleads to a substantially uniform contact between the template and thecured liquid. Such a system may require a large separation force toseparate the template from the cured liquid. In the case of a flexibletemplate or substrate, the separation, in one embodiment, is performedusing a “peeling process.” However, use of a flexible template orsubstrate may be undesirable for high-resolution overlay alignment. Inthe case of a quartz template and a silicon substrate, a peeling processmay be difficult to implement. In one embodiment, a “peel and pull”process is performed to separate the template from an imprinted layer.An embodiment of a peel and pull process is illustrated in FIGS. 33A,33B, and 33C.

FIG. 33A depicts a template 12 embedded in curable liquid 40 aftercuring. After curing of curable liquid 40, either template 12 orsubstrate 20 may be tilted to intentionally induce an angle 3604 betweentemplate 12 and substrate 20, as depicted in FIG. 33B. A pre-calibrationstage, either coupled to template 12 or substrate 20 may be used toinduce a tilt between template 12 and curable liquid 40. The relativelateral motion between template 12 and substrate 20 may be insignificantduring the tilting motion if the tilting axis is located close to thetemplate-substrate interface. Once angle 3604 between template 12 andsubstrate 20 is large enough, template 12 may be separated fromsubstrate 20 using only Z-axis motion (i.e., vertical motion). This peeland pull method may result in desired portions 44 being left intact on atransfer layer 18 and substrate 20 without undesirable shearing,depicted in FIG. 33C.

Electrostatic Curing Process

In addition to the above-described embodiments, embodiments describedherein include forming patterned structures by using electric fields.Cured layers formed using electric fields to induce a pattern in thecured layer may be used for single imprinting or step and repeatprocesses.

FIG. 34 depicts an embodiment of template 1200 and substrate 1202.Template 1200, in one embodiment, is formed from a material that istransparent to activating light to allow curing of the activating lightcurable liquid by exposure to activating light. Forming template 1200from a transparent material also allows the use of established opticaltechniques to measure the gap between template 1200 and substrate 1202and to measure overlay marks to perform overlay alignment andmagnification correction during formation of the structures. Template1200 is also thermally and mechanically stable to providenano-resolution patterning capability. Template 1200 includes anelectrically conducting material and/or layer 1204 to allow electricfields to be generated at template-substrate interface.

In one embodiment, a blank of fused silica (e.g., quartz) is used as thematerial for base 1206 of template 1200. Indium tin oxide (ITO) isdeposited onto base 1206. ITO is transparent to visible and UV light andis a conducting material. ITO may be patterned using high-resolutionelectron beam lithography. A low-surface energy coating, as previouslydescribed, may be coated onto template 1200 to improve the releasecharacteristics between template 1200 and the polymerized composition.Substrate 1202 may include standard wafer materials, such as Si, GaAs,SiGeC and InP. A UV curable liquid and/or a thermally curable liquid maybe used as activating light curable liquid 1208. In an embodiment,activating light curable liquid 1208 may be spin coated onto the wafer1210. In another embodiment, a predetermined volume of activating lightcurable liquid 1208 may be dispensed onto substrate 1202 in apredetermined pattern, as described herein. In some embodiments,transfer layer 1212 may be placed between wafer 1210 and activatinglight curable liquid 1208. Transfer layer 1212 material properties andthickness may be chosen to allow for the creation of high-aspect ratiostructures from low-aspect ratio structures created in the cured liquidmaterial. Connecting ITO to a voltage source 1214 may generate anelectric field between template 1200 and substrate 1202.

In FIGS. 35A-35D and FIGS. 36A-36C, two embodiments of theabove-described process are illustrated. In each embodiment, a desireduniform gap may be maintained between template 1200 and substrate 1202.An electric field of the desired magnitude may be applied resulting inthe attraction of activating light curable liquid 1208 towards theraised portions 1216 of template 1200. In FIGS. 35A-35D, the gap andfield magnitudes are such that activating light curable liquid 1208makes direct contact and adheres to template 1200. A curing agent (e.g.,activating light 1218 and/or heat) may be used to cure the liquid. Oncedesired structures have been formed, template 1200 may be separated fromsubstrate 1202 by methods described herein.

In FIGS. 36A-36C, the gap and field magnitudes may be chosen such thatactivating light curable liquid 1208 achieves a topography that isessentially the same as that of template 1200. This topography may beachieved without making direct contact with template 1200. A curingagent (e.g. activating light 1218) may be used to cure the liquid. Inthe embodiment of FIGS. 35A-35D and FIGS. 36A-36C, a subsequent etchprocess may be used to remove the cured material 1220. A further etchmay also be used if transfer layer 1212 is present between curedmaterial 1220 and wafer 1210, as depicted in FIGS. 35A-35D and FIGS.36A-36C.

In another embodiment, FIG. 37A depicts an electrically conductivetemplate that includes a continuous layer of electrically conductiveportions 1504 coupled to non-conductive bases 1502. As shown in FIG. 37Bthe non-conductive portions 1502 of the template are isolated from eachother by the conductive bases 1504. The template may be used in a“positive” imprint process, as described above.

Use of electric fields allows lithographic patterned structures to beformed, in some instances in a time of less than about 1 second. Thestructures generally have sizes of tens of nanometers. In oneembodiment, curing an activating light curable liquid in the presence ofelectric fields creates a patterned layer on a substrate. The pattern iscreated by placing a template with specific nanometer-scale topographyat a controlled distance (e.g., within nanometers) from the surface of athin layer of the curable liquid on a substrate. If all or a portion ofthe desired structures are regularly repeating patterns (such as anarray of dots), the pattern on the template may be considerably largerthan the size of the desired repeating structures.

The replication of the pattern on the template may be achieved byapplying an electric field between the template and the substrate.Because the liquid and air (or vacuum) have different dielectricconstants and the electric field varies locally due to the presence ofthe topography of the template, an electrostatic force may be generatedthat attracts regions of the liquid toward the template. Surface tensionor capillary pressures tend to stabilize the film. At high electricfield strengths, the activating light curable liquid may be made toattach to the template and de-wet from the substrate at certain points.However, the attachment of the liquid film will occur provided the ratioof electrostatic forces is comparable to the capillary forces, which ismeasured by the dimensionless number A. The magnitude of theelectrostatic force is approximately εE²d², where ε is the permittivityof vacuum, E is the magnitude of the electric field, and d is thefeature size. The magnitude of the capillary forces is approximately γd,where γ is the liquid-gas surface tension. The ratio of these two forcesis Λ=εE²d/γ. In order to deform the interface and cause it to attach tothe upper surface, the electric field must be such that L isapproximately unity. The precise value depends on the details of thetopography of the plates and the ratio of liquid-gas permittivities andheights, but this number will be O(1). Thus, the electric field isapproximately given by E˜(γ/εd)^(1/2). This activating light curableliquid may be hardened in place by polymerization of the composition.The template may be treated with a low energy self-assembled monolayerfilm (e.g., a fluorinated surfactant) to aid in detachment of thetemplate from the polymerized composition.

An example of the above approximations follows: For d=100 nm and γ=30mJ/m and ε=8.85×10-12 C²/J-m, E=1.8×10⁸ V/m, which corresponds to apotential difference between the plates of 18V if the plate spacing is100 nm or 180 if the plate spacing is 1000 nm. Note that the featuresize d˜γ/εE², which means that the size of the feature decreases withthe square of the electric field. Thus, 50 nm features would requirevoltages on the order of 25 or 250V for 100 and 1000 nm plate spacings,respectively.

It may be possible to control the electric field, the design of thetopography of the template and the proximity of the template to theliquid surface so as to create a pattern in the activating light curableliquid that does not come into contact with the surface of the template.This technique may eliminate the need for mechanical separation of thetemplate from the polymerized composition. This technique may alsoeliminate a potential source of defects in the pattern. In the absenceof contact, however, the liquid may not form sharp, high-resolutionstructures that are as well defined as in the case of contact. This maybe addressed by first creating structures in the activating lightcurable liquid that are partially defined at a given electric field.Subsequently, the gap may be increased between the template andsubstrate while simultaneously increasing the magnitude of the electricfield to “draw-out” the liquid to form clearly defined structureswithout requiring contact.

The activating light curable liquid may be deposited on top of atransfer layer as previously described. Such a bi-layer process allowslow aspect ratio, high-resolution structures formed using electricalfields to be followed by an etch process to yield high-aspect ratio,high-resolution structures. Such a bi-layer process may also be used toperform a “metal lift-off process” to deposit a metal on the substratesuch that the metal is left behind after lift-off in the trench areas ofthe originally created structures.

Using a low viscosity activating light curable liquid, pattern formationusing electric fields may be fast (e.g., less than about 1 sec.), andthe structure may be rapidly cured. Avoiding temperature variations inthe substrate and the activating light curable liquid may also avoidundesirable pattern distortion that makes nano-resolution layer-to-layeralignment impractical. In addition, as mentioned above, it is possibleto quickly form a pattern without contact with the template, thuseliminating defects associated with imprint methods that require directcontact.

In this patent application, certain U.S. patents and U.S. patentapplications have been incorporated by reference. The text of such U.S.patents, and U.S. patent applications is, however, only incorporated byreference to the extent that no conflict exists between such text andthe other statements and drawings set forth herein. In the event of suchconflict, U.S. patents and U.S. patent applications are specifically notincorporated by reference in this patent.

While this invention has been described with references to variousillustrative embodiments, the description is not intended to beconstrued in a limiting sense. Various modifications and combinations ofthe illustrative embodiments, as well as other embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto the description. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. An imprint lithography system, comprising: a body; a patternedtemplate comprising a patterning area and a template alignment mark,wherein the patterning area comprises a plurality of recesses extendingfrom a first surface of the template toward an opposing second surfaceof the template, and wherein a first alignment mark is defined by therecesses in the patterning area of the template, and wherein thetemplate alignment mark is a grating structure; a stage coupled to thebody, wherein the stage is configured to support a substrate; an imprinthead coupled to the body, wherein the imprint head is configured to holdthe patterned template proximate to the substrate during use; a liquiddispenser coupled to the body, wherein the liquid dispenser isconfigured to dispense an activating light curable liquid onto at leasta portion of the substrate during use; an activating light sourceoptically coupled to the body, wherein the activating light source isconfigured to direct activating light through the patterned templateduring use; an analyzing light source optically coupled to a portion ofthe template a detector optically coupled to the template, wherein thedetector is configured to measure multiple individual wavelengths oflight reflected from the substrate.
 2. The system of claim 1, whereinthe template alignment mark and the substrate alignment mark eachcomprise a grating having a spacing of between about 1 μm to about 3 μm.3. The system of claim 1, wherein the template alignment mark and thesubstrate alignment mark each comprise a grating having a spacing ofless than about 1 μm.
 4. The system of claim 1, wherein the templatealignment mark and the substrate alignment mark each comprise a gratinghaving a spacing between about 100 and 1000 nm.
 5. The system of claim1, wherein the template alignment mark and the substrate alignment markeach comprise a first grating having a spacing of between about 1 μm toabout 3 μm and a second grating having a spacing between about 100 and1000 nm.
 6. The system of claim 1, wherein the template alignment markand the substrate alignment mark each comprise a first axis grating anda second axis grating, wherein the first axis grating is perpendicularto the second axis grating.
 7. The system of claim 1, wherein thedetector comprises an array camera.
 8. The system of claim 1, whereinthe detector comprises an array camera detector having a resolutioncapable of resolving different wavelengths of light reflected from thesubstrate at a non-zero order.
 9. The system of claim 1, wherein thedetector comprises a spectrophotometer.
 10. The system of claim 1,wherein the detector comprises a non achromatic lens coupled to an arraycamera.
 11. The system of claim 1, wherein the detector comprises aspectrophotometer, and wherein the spectrophotometer is opticallycoupled to light produced by the analyzing light source and reflectedoff of the substrate by a fiber optic cable.
 12. The system of claim 1,wherein the analyzing light source is configured to apply a beam oflight to the template substantially normal to a plane defined by thesubstrate.
 13. The system of claim 1, wherein the analyzing light sourceis configured to apply a beam of light to the template at an angle thatis substantially non-normal to a plane defined by the template.
 14. Thesystem of claim 1, further comprising a force detector coupled to theimprint head, wherein the force detector is configured to determine aresistive force applied to the template by the applied liquid when thetemplate contacts the applied liquid.
 15. The system of claim 1, furthercomprising a support structure coupled to the imprint head and to thestage, wherein the support structure comprises a material having alinear thermal expansion coefficient of less than about 20 ppm/° C. atabout 25° C.
 16. The system of claim 1, further comprising an enclosurearound at least the imprint head and the stage, and a temperaturecontrol system, wherein the temperature control system is configure toinhibit temperature variations of greater than about 1° C. within theenclosure during use.
 17. The system of claim 1, wherein at least aportion of the first surface of the patterned template comprises asurface treatment layer.